diff --git a/entrypoint.go b/entrypoint.go
index cb83d75..3c8ddf6 100644
--- a/entrypoint.go
+++ b/entrypoint.go
@@ -15,12 +15,14 @@ import (
 	"cloud.o-forge.io/core/oc-lib/dbs/mongo"
 	"cloud.o-forge.io/core/oc-lib/logs"
 	"cloud.o-forge.io/core/oc-lib/models"
+	"cloud.o-forge.io/core/oc-lib/models/booking"
 	"cloud.o-forge.io/core/oc-lib/models/collaborative_area"
 	"cloud.o-forge.io/core/oc-lib/models/collaborative_area/rules/rule"
 	"cloud.o-forge.io/core/oc-lib/models/compute_units"
 	"cloud.o-forge.io/core/oc-lib/models/order"
 	"cloud.o-forge.io/core/oc-lib/models/peer"
 	"cloud.o-forge.io/core/oc-lib/models/resources"
+	"cloud.o-forge.io/core/oc-lib/models/resources/purchase_resource"
 	"cloud.o-forge.io/core/oc-lib/models/utils"
 	w2 "cloud.o-forge.io/core/oc-lib/models/workflow"
 	"cloud.o-forge.io/core/oc-lib/models/workflow_execution"
@@ -53,6 +55,7 @@ const (
 	BOOKING                         = tools.BOOKING
 	ORDER                           = tools.ORDER
 	COMPUTE_UNITS                   = tools.COMPUTE_UNITS
+	PURCHASE_RESOURCE               = tools.PURCHASE_RESOURCE
 )
 
 // will turn into standards api hostnames
@@ -585,3 +588,17 @@ func (l *LibData) ToComputeUnits() *compute_units.ComputeUnits {
 	}
 	return nil
 }
+
+func (l *LibData) ToBookings() *booking.Booking {
+	if l.Data.GetAccessor(nil).GetType() == tools.BOOKING {
+		return l.Data.(*booking.Booking)
+	}
+	return nil
+}
+
+func (l *LibData) ToPurchasedResource() *purchase_resource.PurchaseResource {
+	if l.Data.GetAccessor(nil).GetType() == tools.COMPUTE_UNITS {
+		return l.Data.(*purchase_resource.PurchaseResource)
+	}
+	return nil
+}
diff --git a/models/bill/bill.go b/models/bill/bill.go
new file mode 100644
index 0000000..760fcc5
--- /dev/null
+++ b/models/bill/bill.go
@@ -0,0 +1,25 @@
+package bill
+
+import (
+	"cloud.o-forge.io/core/oc-lib/models/utils"
+	"cloud.o-forge.io/core/oc-lib/tools"
+)
+
+/*
+* Bill is a struct that represents when emit billing
+ */
+type Bill struct {
+	utils.AbstractObject
+}
+
+func (r *Bill) StoreDraftDefault() {
+	r.IsDraft = true
+}
+
+func (r *Bill) CanDelete() bool {
+	return r.IsDraft // only draft ComputeUnits can be deleted
+}
+
+func (d *Bill) GetAccessor(request *tools.APIRequest) utils.Accessor {
+	return NewAccessor(request) // Create a new instance of the accessor
+}
diff --git a/models/bill/bill_mongo_accessor.go b/models/bill/bill_mongo_accessor.go
new file mode 100644
index 0000000..5141ef0
--- /dev/null
+++ b/models/bill/bill_mongo_accessor.go
@@ -0,0 +1,63 @@
+package bill
+
+import (
+	"cloud.o-forge.io/core/oc-lib/dbs"
+	"cloud.o-forge.io/core/oc-lib/logs"
+	"cloud.o-forge.io/core/oc-lib/models/utils"
+	"cloud.o-forge.io/core/oc-lib/tools"
+)
+
+type billMongoAccessor struct {
+	utils.AbstractAccessor // AbstractAccessor contains the basic fields of an accessor (model, caller)
+}
+
+// New creates a new instance of the billMongoAccessor
+func NewAccessor(request *tools.APIRequest) *billMongoAccessor {
+	return &billMongoAccessor{
+		AbstractAccessor: utils.AbstractAccessor{
+			Logger:  logs.CreateLogger(tools.COMPUTE_UNITS.String()), // Create a logger with the data type
+			Request: request,
+			Type:    tools.COMPUTE_UNITS,
+		},
+	}
+}
+
+/*
+* Nothing special here, just the basic CRUD operations
+ */
+func (a *billMongoAccessor) DeleteOne(id string) (utils.DBObject, int, error) {
+	return utils.GenericDeleteOne(id, a)
+}
+
+func (a *billMongoAccessor) UpdateOne(set utils.DBObject, id string) (utils.DBObject, int, error) {
+	// should verify if a source is existing...
+	return utils.GenericUpdateOne(set, id, a, &Bill{})
+}
+
+func (a *billMongoAccessor) StoreOne(data utils.DBObject) (utils.DBObject, int, error) {
+	return utils.GenericStoreOne(data.(*Bill), a)
+}
+
+func (a *billMongoAccessor) CopyOne(data utils.DBObject) (utils.DBObject, int, error) {
+	return utils.GenericStoreOne(data.(*Bill), a)
+}
+
+func (a *billMongoAccessor) LoadOne(id string) (utils.DBObject, int, error) {
+	return utils.GenericLoadOne[*Bill](id, func(d utils.DBObject) (utils.DBObject, int, error) {
+		return d, 200, nil
+	}, a)
+}
+
+func (a *billMongoAccessor) LoadAll(isDraft bool) ([]utils.ShallowDBObject, int, error) {
+	return utils.GenericLoadAll[*Bill](a.getExec(), isDraft, a)
+}
+
+func (a *billMongoAccessor) Search(filters *dbs.Filters, search string, isDraft bool) ([]utils.ShallowDBObject, int, error) {
+	return utils.GenericSearch[*Bill](filters, search, (&Bill{}).GetObjectFilters(search), a.getExec(), isDraft, a)
+}
+
+func (a *billMongoAccessor) getExec() func(utils.DBObject) utils.ShallowDBObject {
+	return func(d utils.DBObject) utils.ShallowDBObject {
+		return d
+	}
+}
diff --git a/models/common/pricing/interfaces.go b/models/common/pricing/interfaces.go
index a7605f9..fdbc62d 100755
--- a/models/common/pricing/interfaces.go
+++ b/models/common/pricing/interfaces.go
@@ -9,7 +9,8 @@ import (
 type PricedItemITF interface {
 	GetID() string
 	GetType() tools.DataType
-	IsPurchased() bool
+	IsPurchasable() bool
+	IsBooked() bool
 	GetCreatorID() string
 	GetLocationStart() *time.Time
 	SetLocationStart(start time.Time)
diff --git a/models/common/pricing/pricing_profile.go b/models/common/pricing/pricing_profile.go
index fa81629..79aacb5 100755
--- a/models/common/pricing/pricing_profile.go
+++ b/models/common/pricing/pricing_profile.go
@@ -6,7 +6,8 @@ import (
 
 type PricingProfileITF interface {
 	GetPrice(quantity float64, val float64, start time.Time, end time.Time, params ...string) (float64, error)
-	IsPurchased() bool
+	IsPurchasable() bool
+	IsBooked() bool
 	GetOverrideStrategyValue() int
 }
 
diff --git a/models/common/pricing/pricing_strategy.go b/models/common/pricing/pricing_strategy.go
index 94576bb..fee356f 100755
--- a/models/common/pricing/pricing_strategy.go
+++ b/models/common/pricing/pricing_strategy.go
@@ -7,21 +7,65 @@ import (
 	"time"
 )
 
+type BillingStrategy int // BAM BAM
+
+// should except... on
+const (
+	BILL_ONCE BillingStrategy = iota // is a permanent buying ( predictible )
+	BILL_PER_WEEK
+	BILL_PER_MONTH
+	BILL_PER_YEAR
+)
+
+func (t BillingStrategy) IsBillingStrategyAllowed(bs int) (BillingStrategy, bool) {
+	switch t {
+	case BILL_ONCE:
+		return BILL_ONCE, bs == 0
+	case BILL_PER_WEEK:
+	case BILL_PER_MONTH:
+	case BILL_PER_YEAR:
+		return t, bs != 0
+	}
+	return t, false
+}
+
+func (t BillingStrategy) String() string {
+	return [...]string{"BILL_ONCE", "BILL_PER_WEEK", "BILL_PER_MONTH", "BILL_PER_YEAR"}[t]
+}
+
+func BillingStrategyList() []BillingStrategy {
+	return []BillingStrategy{BILL_ONCE, BILL_PER_WEEK, BILL_PER_MONTH, BILL_PER_YEAR}
+}
+
 type BuyingStrategy int
 
 // should except... on
 const (
-	UNLIMITED BuyingStrategy = iota
-	SUBSCRIPTION
-	PAY_PER_USE
+	PERMANENT              BuyingStrategy = iota // is a permanent buying ( predictible )
+	UNDEFINED_SUBSCRIPTION                       // a endless subscription ( unpredictible )
+	SUBSCRIPTION                                 // a defined subscription ( predictible )
+	// PAY_PER_USE                                  // per request. ( unpredictible )
 )
 
 func (t BuyingStrategy) String() string {
-	return [...]string{"UNLIMITED", "SUBSCRIPTION", "PAY PER USE"}[t]
+	return [...]string{"PERMANENT", "UNDEFINED_SUBSCRIPTION", "SUBSCRIPTION"}[t]
+}
+
+func (t BuyingStrategy) IsBillingStrategyAllowed(bs BillingStrategy) (BillingStrategy, bool) {
+	switch t {
+	case PERMANENT:
+		return BILL_ONCE, bs == BILL_ONCE
+	case UNDEFINED_SUBSCRIPTION:
+		return BILL_PER_MONTH, bs != BILL_ONCE
+	case SUBSCRIPTION:
+		/*case PAY_PER_USE:
+		return bs, true*/
+	}
+	return bs, false
 }
 
 func BuyingStrategyList() []BuyingStrategy {
-	return []BuyingStrategy{UNLIMITED, SUBSCRIPTION, PAY_PER_USE}
+	return []BuyingStrategy{PERMANENT, UNDEFINED_SUBSCRIPTION, SUBSCRIPTION}
 }
 
 type Strategy interface {
@@ -118,7 +162,7 @@ type PricingStrategy[T Strategy] struct {
 func (p PricingStrategy[T]) GetPrice(amountOfData float64, bookingTimeDuration float64, start time.Time, end *time.Time) (float64, error) {
 	if p.BuyingStrategy == SUBSCRIPTION {
 		return BookingEstimation(p.GetTimePricingStrategy(), p.Price*float64(amountOfData), bookingTimeDuration, start, end)
-	} else if p.BuyingStrategy == UNLIMITED {
+	} else if p.BuyingStrategy == PERMANENT {
 		return p.Price, nil
 	}
 	return p.Price * float64(amountOfData), nil
diff --git a/models/common/pricing/tests/pricing_test.go b/models/common/pricing/tests/pricing_test.go
index 105b5d1..2aee55f 100644
--- a/models/common/pricing/tests/pricing_test.go
+++ b/models/common/pricing/tests/pricing_test.go
@@ -15,9 +15,9 @@ func (d DummyStrategy) GetStrategy() string   { return "DUMMY" }
 func (d DummyStrategy) GetStrategyValue() int { return int(d) }
 
 func TestBuyingStrategy_String(t *testing.T) {
-	assert.Equal(t, "UNLIMITED", pricing.UNLIMITED.String())
+	assert.Equal(t, "UNLIMITED", pricing.PERMANENT.String())
 	assert.Equal(t, "SUBSCRIPTION", pricing.SUBSCRIPTION.String())
-	assert.Equal(t, "PAY PER USE", pricing.PAY_PER_USE.String())
+	//assert.Equal(t, "PAY PER USE", pricing.PAY_PER_USE.String())
 }
 
 func TestBuyingStrategyList(t *testing.T) {
@@ -116,13 +116,13 @@ func TestPricingStrategy_GetPrice(t *testing.T) {
 	assert.True(t, p > 0)
 
 	// UNLIMITED case
-	ps.BuyingStrategy = pricing.UNLIMITED
+	ps.BuyingStrategy = pricing.PERMANENT
 	p, err = ps.GetPrice(10, 0, start, &end)
 	assert.NoError(t, err)
 	assert.Equal(t, 5.0, p)
 
 	// PAY_PER_USE case
-	ps.BuyingStrategy = pricing.PAY_PER_USE
+	//ps.BuyingStrategy = pricing.PAY_PER_USE
 	p, err = ps.GetPrice(3, 0, start, &end)
 	assert.NoError(t, err)
 	assert.Equal(t, 15.0, p)
diff --git a/models/models.go b/models/models.go
index 41fdffb..8674820 100644
--- a/models/models.go
+++ b/models/models.go
@@ -2,6 +2,7 @@ package models
 
 import (
 	"cloud.o-forge.io/core/oc-lib/logs"
+	"cloud.o-forge.io/core/oc-lib/models/bill"
 	"cloud.o-forge.io/core/oc-lib/models/compute_units"
 	"cloud.o-forge.io/core/oc-lib/models/order"
 	"cloud.o-forge.io/core/oc-lib/models/resources/purchase_resource"
@@ -40,6 +41,7 @@ var ModelsCatalog = map[string]func() utils.DBObject{
 	tools.ORDER.String():               func() utils.DBObject { return &order.Order{} },
 	tools.PURCHASE_RESOURCE.String():   func() utils.DBObject { return &purchase_resource.PurchaseResource{} },
 	tools.COMPUTE_UNITS.String():       func() utils.DBObject { return &compute_units.ComputeUnits{} },
+	tools.BILL.String():                func() utils.DBObject { return &bill.Bill{} },
 }
 
 // Model returns the model object based on the model type
diff --git a/models/order/order.go b/models/order/order.go
index 585ce1e..1a90111 100644
--- a/models/order/order.go
+++ b/models/order/order.go
@@ -265,7 +265,7 @@ func (d *PeerOrder) Pay(request *tools.APIRequest, response chan *PeerOrder, wg
 		d.Status = enum.PAID // TO REMOVE LATER IT'S A MOCK
 		if d.Status == enum.PAID {
 			for _, b := range d.Items {
-				if !b.Item.IsPurchased() {
+				if !b.Item.IsPurchasable() {
 					continue
 				}
 				accessor := purchase_resource.NewAccessor(request)
diff --git a/models/resources/compute.go b/models/resources/compute.go
index d6ff81b..fb3ab95 100755
--- a/models/resources/compute.go
+++ b/models/resources/compute.go
@@ -80,8 +80,15 @@ type ComputeResourcePricingProfile struct {
 	RAMPrice   float64            `json:"ram_price" bson:"ram_price" default:"-1"`            // RAMPrice is the price of the RAM
 }
 
-func (p *ComputeResourcePricingProfile) IsPurchased() bool {
-	return p.Pricing.BuyingStrategy != pricing.PAY_PER_USE
+func (p *ComputeResourcePricingProfile) IsPurchasable() bool {
+	return p.Pricing.BuyingStrategy != pricing.UNDEFINED_SUBSCRIPTION
+}
+
+func (p *ComputeResourcePricingProfile) IsBooked() bool {
+	if p.Pricing.BuyingStrategy == pricing.PERMANENT {
+		p.Pricing.BuyingStrategy = pricing.SUBSCRIPTION
+	}
+	return true
 }
 
 func (p *ComputeResourcePricingProfile) GetOverrideStrategyValue() int {
diff --git a/models/resources/data.go b/models/resources/data.go
index e9ec3df..b0c47ac 100755
--- a/models/resources/data.go
+++ b/models/resources/data.go
@@ -137,8 +137,13 @@ func (p *DataResourcePricingProfile) GetPrice(amountOfData float64, explicitDura
 	return p.Pricing.GetPrice(amountOfData, explicitDuration, start, &end)
 }
 
-func (p *DataResourcePricingProfile) IsPurchased() bool {
-	return p.Pricing.BuyingStrategy != pricing.PAY_PER_USE
+func (p *DataResourcePricingProfile) IsPurchasable() bool {
+	return p.Pricing.BuyingStrategy != pricing.UNDEFINED_SUBSCRIPTION
+}
+
+func (p *DataResourcePricingProfile) IsBooked() bool {
+	// TODO WHAT ABOUT PAY PER USE... it's a complicate CASE
+	return p.Pricing.BuyingStrategy != pricing.PERMANENT
 }
 
 type PricedDataResource struct {
diff --git a/models/resources/priced_resource.go b/models/resources/priced_resource.go
index 5265cce..c65f697 100755
--- a/models/resources/priced_resource.go
+++ b/models/resources/priced_resource.go
@@ -35,11 +35,18 @@ func (abs *PricedResource) GetCreatorID() string {
 	return abs.CreatorID
 }
 
-func (abs *PricedResource) IsPurchased() bool {
+func (abs *PricedResource) IsPurchasable() bool {
 	if abs.SelectedPricing == nil {
 		return false
 	}
-	return (abs.SelectedPricing).IsPurchased()
+	return (abs.SelectedPricing).IsPurchasable()
+}
+
+func (abs *PricedResource) IsBooked() bool {
+	if abs.SelectedPricing == nil {
+		return false
+	}
+	return (abs.SelectedPricing).IsBooked()
 }
 
 func (abs *PricedResource) GetLocationEnd() *time.Time {
diff --git a/models/resources/processing.go b/models/resources/processing.go
index c2f9e38..4661689 100755
--- a/models/resources/processing.go
+++ b/models/resources/processing.go
@@ -77,8 +77,12 @@ type ProcessingResourcePricingProfile struct {
 	pricing.AccessPricingProfile[pricing.TimePricingStrategy] // AccessPricingProfile is the pricing profile of a data it means that we can access the data for an amount of time
 }
 
-func (p *ProcessingResourcePricingProfile) IsPurchased() bool {
-	return p.Pricing.BuyingStrategy != pricing.PAY_PER_USE
+func (p *ProcessingResourcePricingProfile) IsPurchasable() bool {
+	return p.Pricing.BuyingStrategy != pricing.UNDEFINED_SUBSCRIPTION
+}
+
+func (p *ProcessingResourcePricingProfile) IsBooked() bool {
+	return p.Pricing.BuyingStrategy != pricing.PERMANENT
 }
 
 func (p *ProcessingResourcePricingProfile) GetPrice(amountOfData float64, val float64, start time.Time, end time.Time, params ...string) (float64, error) {
diff --git a/models/resources/resource.go b/models/resources/resource.go
index c57a23d..45a5a62 100755
--- a/models/resources/resource.go
+++ b/models/resources/resource.go
@@ -52,7 +52,8 @@ type AbstractInstanciatedResource[T ResourceInstanceITF] struct {
 	Instances        []T `json:"instances,omitempty" bson:"instances,omitempty"` // Bill is the bill of the resource            // Bill is the bill of the resource
 }
 
-func (abs *AbstractInstanciatedResource[T]) ConvertToPricedResource(t tools.DataType, request *tools.APIRequest, buyingStrategy int, pricingStrategy int) pricing.PricedItemITF {
+func (abs *AbstractInstanciatedResource[T]) ConvertToPricedResource(
+	t tools.DataType, request *tools.APIRequest, buyingStrategy int, pricingStrategy int) pricing.PricedItemITF {
 	instances := map[string]string{}
 	profiles := []pricing.PricingProfileITF{}
 	for _, instance := range abs.Instances {
diff --git a/models/resources/storage.go b/models/resources/storage.go
index 481f326..14d578c 100755
--- a/models/resources/storage.go
+++ b/models/resources/storage.go
@@ -152,8 +152,15 @@ type StorageResourcePricingProfile struct {
 	pricing.ExploitPricingProfile[StorageResourcePricingStrategy] // ExploitPricingProfile is the pricing profile of a storage it means that we exploit the resource for an amount of continuous time
 }
 
-func (p *StorageResourcePricingProfile) IsPurchased() bool {
-	return p.Pricing.BuyingStrategy != pricing.PAY_PER_USE
+func (p *StorageResourcePricingProfile) IsPurchasable() bool {
+	return p.Pricing.BuyingStrategy != pricing.UNDEFINED_SUBSCRIPTION
+}
+
+func (p *StorageResourcePricingProfile) IsBooked() bool {
+	if p.Pricing.BuyingStrategy == pricing.PERMANENT {
+		p.Pricing.BuyingStrategy = pricing.SUBSCRIPTION
+	}
+	return true
 }
 
 func (p *StorageResourcePricingProfile) GetPrice(amountOfData float64, val float64, start time.Time, end time.Time, params ...string) (float64, error) {
diff --git a/models/resources/tests/data_test.go b/models/resources/tests/data_test.go
index 0665519..af7cc2e 100644
--- a/models/resources/tests/data_test.go
+++ b/models/resources/tests/data_test.go
@@ -76,11 +76,8 @@ func TestDataResourcePricingStrategy_GetQuantity(t *testing.T) {
 
 func TestDataResourcePricingProfile_IsPurchased(t *testing.T) {
 	profile := &resources.DataResourcePricingProfile{}
-	profile.Pricing.BuyingStrategy = pricing.PAY_PER_USE
-	assert.False(t, profile.IsPurchased())
-
 	profile.Pricing.BuyingStrategy = pricing.SUBSCRIPTION
-	assert.True(t, profile.IsPurchased())
+	assert.True(t, profile.IsPurchasable())
 }
 
 func TestPricedDataResource_GetPrice(t *testing.T) {
diff --git a/models/resources/tests/priced_resource_test.go b/models/resources/tests/priced_resource_test.go
index 61616a8..d47d26e 100644
--- a/models/resources/tests/priced_resource_test.go
+++ b/models/resources/tests/priced_resource_test.go
@@ -22,7 +22,7 @@ type MockPricingProfile struct {
 	ReturnCost float64
 }
 
-func (m *MockPricingProfile) IsPurchased() bool {
+func (m *MockPricingProfile) IsPurchasable() bool {
 	return m.Purchased
 }
 
@@ -49,13 +49,13 @@ func TestGetIDAndCreatorAndType(t *testing.T) {
 func TestIsPurchased(t *testing.T) {
 	t.Run("nil selected pricing returns false", func(t *testing.T) {
 		r := &resources.PricedResource{}
-		assert.False(t, r.IsPurchased())
+		assert.False(t, r.IsPurchasable())
 	})
 
 	t.Run("returns true if pricing profile is purchased", func(t *testing.T) {
 		mock := &MockPricingProfile{Purchased: true}
 		r := &resources.PricedResource{SelectedPricing: mock}
-		assert.True(t, r.IsPurchased())
+		assert.True(t, r.IsPurchasable())
 	})
 }
 
diff --git a/models/resources/tests/processing_test.go b/models/resources/tests/processing_test.go
index 06e12c1..ce3de34 100644
--- a/models/resources/tests/processing_test.go
+++ b/models/resources/tests/processing_test.go
@@ -95,21 +95,12 @@ func TestProcessingResourcePricingProfile_GetPrice(t *testing.T) {
 }
 
 func TestProcessingResourcePricingProfile_IsPurchased(t *testing.T) {
-	nonPurchased := &ProcessingResourcePricingProfile{
-		AccessPricingProfile: pricing.AccessPricingProfile[pricing.TimePricingStrategy]{
-			Pricing: pricing.PricingStrategy[pricing.TimePricingStrategy]{
-				BuyingStrategy: pricing.PAY_PER_USE,
-			},
-		},
-	}
-	assert.False(t, nonPurchased.IsPurchased())
-
 	purchased := &ProcessingResourcePricingProfile{
 		AccessPricingProfile: pricing.AccessPricingProfile[pricing.TimePricingStrategy]{
 			Pricing: pricing.PricingStrategy[pricing.TimePricingStrategy]{
-				BuyingStrategy: pricing.UNLIMITED,
+				BuyingStrategy: pricing.PERMANENT,
 			},
 		},
 	}
-	assert.True(t, purchased.IsPurchased())
+	assert.True(t, purchased.IsPurchasable())
 }
diff --git a/models/resources/tests/storage_test.go b/models/resources/tests/storage_test.go
index 1a42978..2e1d0e2 100644
--- a/models/resources/tests/storage_test.go
+++ b/models/resources/tests/storage_test.go
@@ -2,10 +2,8 @@ package resources_test
 
 import (
 	"testing"
-	"time"
 
 	"cloud.o-forge.io/core/oc-lib/models/common/models"
-	"cloud.o-forge.io/core/oc-lib/models/common/pricing"
 	"cloud.o-forge.io/core/oc-lib/tools"
 	"github.com/stretchr/testify/assert"
 
@@ -107,43 +105,3 @@ func TestPricedStorageResource_GetPrice_NoProfiles(t *testing.T) {
 	_, err := res.GetPrice()
 	assert.Error(t, err)
 }
-
-func TestPricedStorageResource_GetPrice_WithPricing(t *testing.T) {
-	now := time.Now()
-	end := now.Add(2 * time.Hour)
-	profile := &resources.StorageResourcePricingProfile{
-		ExploitPricingProfile: pricing.ExploitPricingProfile[resources.StorageResourcePricingStrategy]{
-			AccessPricingProfile: pricing.AccessPricingProfile[resources.StorageResourcePricingStrategy]{
-				Pricing: pricing.PricingStrategy[resources.StorageResourcePricingStrategy]{
-					BuyingStrategy: pricing.PAY_PER_USE,
-					Price:          42.0,
-				},
-			},
-		},
-	}
-	res := &resources.PricedStorageResource{
-		PricedResource: resources.PricedResource{
-			UsageStart:      &now,
-			UsageEnd:        &end,
-			PricingProfiles: []pricing.PricingProfileITF{profile},
-		},
-		UsageStorageGB: 1.0,
-	}
-	price, err := res.GetPrice()
-	assert.NoError(t, err)
-	assert.Equal(t, 42.0, price)
-}
-
-func TestStorageResourcePricingProfile_IsPurchased(t *testing.T) {
-	p := &resources.StorageResourcePricingProfile{
-		ExploitPricingProfile: pricing.ExploitPricingProfile[resources.StorageResourcePricingStrategy]{
-			AccessPricingProfile: pricing.AccessPricingProfile[resources.StorageResourcePricingStrategy]{
-				Pricing: pricing.PricingStrategy[resources.StorageResourcePricingStrategy]{BuyingStrategy: pricing.PAY_PER_USE},
-			},
-		},
-	}
-	assert.False(t, p.IsPurchased())
-
-	p.Pricing.BuyingStrategy = pricing.UNLIMITED
-	assert.True(t, p.IsPurchased())
-}
diff --git a/models/workflow/workflow.go b/models/workflow/workflow.go
index 5c0b134..d140442 100644
--- a/models/workflow/workflow.go
+++ b/models/workflow/workflow.go
@@ -169,8 +169,8 @@ func (wfa *Workflow) CheckBooking(caller *tools.HTTPCaller) (bool, error) {
 func (wf *Workflow) Planify(start time.Time, end *time.Time, request *tools.APIRequest, buyingStrategy int, pricingStrategy int) (float64, map[tools.DataType]map[string]pricing.PricedItemITF, *Workflow, error) {
 	priceds := map[tools.DataType]map[string]pricing.PricedItemITF{}
 	ps, priceds, err := plan[*resources.ProcessingResource](tools.PROCESSING_RESOURCE, wf, priceds, request,
-		buyingStrategy, pricingStrategy,
-		wf.Graph.IsProcessing, func(res resources.ResourceInterface, priced pricing.PricedItemITF) (time.Time, float64) {
+		buyingStrategy, pricingStrategy, wf.Graph.IsProcessing,
+		func(res resources.ResourceInterface, priced pricing.PricedItemITF) (time.Time, float64) {
 			return start.Add(time.Duration(wf.Graph.GetAverageTimeProcessingBeforeStart(0, res.GetID(), request, buyingStrategy, pricingStrategy)) * time.Second), priced.GetExplicitDurationInS()
 		}, func(started time.Time, duration float64) *time.Time {
 			s := started.Add(time.Duration(duration))
diff --git a/models/workflow_execution/workflow_execution.go b/models/workflow_execution/workflow_execution.go
index ec4c4c4..2cf65e9 100755
--- a/models/workflow_execution/workflow_execution.go
+++ b/models/workflow_execution/workflow_execution.go
@@ -8,6 +8,7 @@ import (
 	"cloud.o-forge.io/core/oc-lib/models/booking"
 	"cloud.o-forge.io/core/oc-lib/models/common/enum"
 	"cloud.o-forge.io/core/oc-lib/models/common/pricing"
+	"cloud.o-forge.io/core/oc-lib/models/resources/purchase_resource"
 	"cloud.o-forge.io/core/oc-lib/models/utils"
 	"cloud.o-forge.io/core/oc-lib/tools"
 	"github.com/google/uuid"
@@ -21,6 +22,7 @@ import (
  */
 type WorkflowExecution struct {
 	utils.AbstractObject                                // AbstractObject contains the basic fields of an object (id, name)
+	PeerBuyByGraph       map[string]map[string][]string `json:"peer_buy_by_graph,omitempty" bson:"peer_buy_by_graph,omitempty"`   // BookByResource is a map of the resource id and the list of the booking id
 	PeerBookByGraph      map[string]map[string][]string `json:"peer_book_by_graph,omitempty" bson:"peer_book_by_graph,omitempty"` // BookByResource is a map of the resource id and the list of the booking id
 	ExecutionsID         string                         `json:"executions_id,omitempty" bson:"executions_id,omitempty"`
 	ExecDate             time.Time                      `json:"execution_date,omitempty" bson:"execution_date,omitempty" validate:"required"` // ExecDate is the execution date of the workflow, is required
@@ -110,10 +112,51 @@ func (d *WorkflowExecution) VerifyAuth(request *tools.APIRequest) bool {
 }
 
 /*
-	booking is an activity reserved for not a long time investment.
-	... purchase is dependant of a one time buying.
-	use of a datacenter or storage can't be buy for permanent.
+booking is an activity reserved for not a long time investment.
+... purchase is dependant of a one time buying.
+use of a datacenter or storage can't be buy for permanent access.
 */
+func (d *WorkflowExecution) Buy(bs pricing.BillingStrategy, executionsID string, wfID string, priceds map[tools.DataType]map[string]pricing.PricedItemITF) []*purchase_resource.PurchaseResource {
+	purchases := d.buyEach(bs, executionsID, wfID, tools.PROCESSING_RESOURCE, priceds[tools.PROCESSING_RESOURCE])
+	purchases = append(purchases, d.buyEach(bs, executionsID, wfID, tools.DATA_RESOURCE, priceds[tools.DATA_RESOURCE])...)
+	return purchases
+}
+
+func (d *WorkflowExecution) buyEach(bs pricing.BillingStrategy, executionsID string, wfID string, dt tools.DataType, priceds map[string]pricing.PricedItemITF) []*purchase_resource.PurchaseResource {
+	items := []*purchase_resource.PurchaseResource{}
+	for itemID, priced := range priceds {
+		if !priced.IsPurchasable() && bs == pricing.BILL_ONCE { // buy only that must be buy
+			continue
+		}
+		if d.PeerBuyByGraph == nil {
+			d.PeerBuyByGraph = map[string]map[string][]string{}
+		}
+		if d.PeerBuyByGraph[priced.GetCreatorID()] == nil {
+			d.PeerBuyByGraph[priced.GetCreatorID()] = map[string][]string{}
+		}
+		if d.PeerBuyByGraph[priced.GetCreatorID()][itemID] == nil {
+			d.PeerBuyByGraph[priced.GetCreatorID()][itemID] = []string{}
+		}
+		start := d.ExecDate
+		if s := priced.GetLocationStart(); s != nil {
+			start = *s
+		}
+		end := start.Add(time.Duration(priced.GetExplicitDurationInS()) * time.Second)
+		bookingItem := &purchase_resource.PurchaseResource{
+			AbstractObject: utils.AbstractObject{
+				UUID: uuid.New().String(),
+				Name: d.GetName() + "_" + executionsID + "_" + wfID,
+			},
+			ResourceID:   priced.GetID(),
+			ResourceType: dt,
+			EndDate:      &end,
+		}
+		items = append(items, bookingItem)
+		d.PeerBuyByGraph[priced.GetCreatorID()][itemID] = append(
+			d.PeerBuyByGraph[priced.GetCreatorID()][itemID], bookingItem.GetID())
+	}
+	return items
+}
 
 func (d *WorkflowExecution) Book(executionsID string, wfID string, priceds map[tools.DataType]map[string]pricing.PricedItemITF) []*booking.Booking {
 	booking := d.bookEach(executionsID, wfID, tools.STORAGE_RESOURCE, priceds[tools.STORAGE_RESOURCE])
@@ -126,6 +169,9 @@ func (d *WorkflowExecution) Book(executionsID string, wfID string, priceds map[t
 func (d *WorkflowExecution) bookEach(executionsID string, wfID string, dt tools.DataType, priceds map[string]pricing.PricedItemITF) []*booking.Booking {
 	items := []*booking.Booking{}
 	for itemID, priced := range priceds {
+		if !priced.IsBooked() { // book only that must be booked
+			continue
+		}
 		if d.PeerBookByGraph == nil {
 			d.PeerBookByGraph = map[string]map[string][]string{}
 		}
diff --git a/models/workflow_execution/workflow_scheduler.go b/models/workflow_execution/workflow_scheduler.go
index 6156176..b0728bc 100755
--- a/models/workflow_execution/workflow_scheduler.go
+++ b/models/workflow_execution/workflow_scheduler.go
@@ -11,6 +11,7 @@ import (
 	"cloud.o-forge.io/core/oc-lib/models/common/enum"
 	"cloud.o-forge.io/core/oc-lib/models/common/pricing"
 	"cloud.o-forge.io/core/oc-lib/models/peer"
+	"cloud.o-forge.io/core/oc-lib/models/resources/purchase_resource"
 	"cloud.o-forge.io/core/oc-lib/models/utils"
 	"cloud.o-forge.io/core/oc-lib/models/workflow"
 	"cloud.o-forge.io/core/oc-lib/tools"
@@ -34,8 +35,9 @@ type WorkflowSchedule struct {
 	DurationS         float64              `json:"duration_s" default:"-1"`               // End is the end time of the schedule
 	Cron              string               `json:"cron,omitempty"`                        // here the cron format : ss mm hh dd MM dw task
 
-	SelectedBuyingStrategy  pricing.BuyingStrategy `json:"selected_buying_strategy"`
-	SelectedPricingStrategy int                    `json:"selected_pricing_strategy"`
+	SelectedBuyingStrategy  pricing.BuyingStrategy  `json:"selected_buying_strategy"`
+	SelectedPricingStrategy int                     `json:"selected_pricing_strategy"`
+	SelectedBillingStrategy pricing.BillingStrategy `json:"selected_billing_strategy"`
 }
 
 func NewScheduler(start string, end string, durationInS float64, cron string) *WorkflowSchedule {
@@ -79,8 +81,10 @@ func (ws *WorkflowSchedule) CheckBooking(wfID string, request *tools.APIRequest)
 	if err != nil {
 		return false, wf, []*WorkflowExecution{}, []*booking.Booking{}, err
 	}
+	purchased := []*purchase_resource.PurchaseResource{}
 	bookings := []*booking.Booking{}
 	for _, exec := range execs {
+		purchased = append(purchased, exec.Buy(ws.SelectedBillingStrategy, ws.UUID, wfID, priceds)...)
 		bookings = append(bookings, exec.Book(ws.UUID, wfID, priceds)...)
 	}
 
diff --git a/tools/enums.go b/tools/enums.go
index 2bb54e0..c0f1d42 100644
--- a/tools/enums.go
+++ b/tools/enums.go
@@ -27,6 +27,7 @@ const (
 	ADMIRALTY_KUBECONFIG
 	ADMIRALTY_NODES
 	COMPUTE_UNITS
+	BILL
 )
 
 var NOAPI = ""
@@ -67,6 +68,7 @@ var DefaultAPI = [...]string{
 	ADMIRALTY_KUBECONFIGAPI,
 	ADMIRALTY_NODESAPI,
 	DATACENTERAPI,
+	NOAPI,
 }
 
 // Bind the standard data name to the data type
@@ -94,6 +96,7 @@ var Str = [...]string{
 	"admiralty_kubeconfig",
 	"admiralty_node",
 	"compute_units",
+	"bill",
 }
 
 func FromInt(i int) string {
@@ -114,5 +117,7 @@ func (d DataType) EnumIndex() int {
 }
 
 func DataTypeList() []DataType {
-	return []DataType{DATA_RESOURCE, PROCESSING_RESOURCE, STORAGE_RESOURCE, COMPUTE_RESOURCE, WORKFLOW_RESOURCE, WORKFLOW, WORKFLOW_EXECUTION, WORKSPACE, PEER, COLLABORATIVE_AREA, RULE, BOOKING, WORKFLOW_HISTORY, WORKSPACE_HISTORY, ORDER, PURCHASE_RESOURCE, ADMIRALTY_SOURCE, ADMIRALTY_TARGET, ADMIRALTY_SECRET, ADMIRALTY_KUBECONFIG, ADMIRALTY_NODES}
+	return []DataType{DATA_RESOURCE, PROCESSING_RESOURCE, STORAGE_RESOURCE, COMPUTE_RESOURCE, WORKFLOW_RESOURCE,
+		WORKFLOW, WORKFLOW_EXECUTION, WORKSPACE, PEER, COLLABORATIVE_AREA, RULE, BOOKING, WORKFLOW_HISTORY, WORKSPACE_HISTORY,
+		ORDER, PURCHASE_RESOURCE, ADMIRALTY_SOURCE, ADMIRALTY_TARGET, ADMIRALTY_SECRET, ADMIRALTY_KUBECONFIG, ADMIRALTY_NODES, COMPUTE_UNITS, BILL}
 }