diff --git a/htdocs/comm/askpricesupplier/class/askpricesupplier.class.php b/htdocs/comm/askpricesupplier/class/askpricesupplier.class.php
index 26d412e87ea..2f563a17b1b 100644
--- a/htdocs/comm/askpricesupplier/class/askpricesupplier.class.php
+++ b/htdocs/comm/askpricesupplier/class/askpricesupplier.class.php
@@ -2649,11 +2649,18 @@ class AskPriceSupplierLine  extends CommonObject
 
         if (empty($this->pa_ht)) $this->pa_ht=0;
 
-        // si prix d'achat non renseigne et utilise pour calcul des marges alors prix achat = prix vente
-        if ($this->pa_ht == 0) {
-        	if ($this->subprice > 0 && (isset($conf->global->ForceBuyingPriceIfNull) && $conf->global->ForceBuyingPriceIfNull == 1))
-        		$this->pa_ht = $this->subprice * (1 - $this->remise_percent / 100);
-        }
+		// if buy price not defined, define buyprice as configured in margin admin
+		if ($this->pa_ht == 0) 
+		{
+			if (($result = $this->defineBuyPrice($this->subprice, $this->remise_percent, $this->fk_product)) < 0)
+			{
+				return $result;
+			}
+			else
+			{
+				$this->pa_ht = $result;
+			}
+		}
 
         // Check parameters
         if ($this->product_type < 0) return -1;
@@ -2817,10 +2824,17 @@ class AskPriceSupplierLine  extends CommonObject
 
 		if (empty($this->pa_ht)) $this->pa_ht=0;
 
-		// si prix d'achat non renseigne et utilise pour calcul des marges alors prix achat = prix vente
-		if ($this->pa_ht == 0) {
-			if ($this->subprice > 0 && (isset($conf->global->ForceBuyingPriceIfNull) && $conf->global->ForceBuyingPriceIfNull == 1))
-				$this->pa_ht = $this->subprice * (1 - $this->remise_percent / 100);
+		// if buy price not defined, define buyprice as configured in margin admin
+		if ($this->pa_ht == 0) 
+		{
+			if (($result = $this->defineBuyPrice($this->subprice, $this->remise_percent, $this->fk_product)) < 0)
+			{
+				return $result;
+			}
+			else
+			{
+				$this->pa_ht = $result;
+			}
 		}
 
         $this->db->begin();
diff --git a/htdocs/comm/propal/class/propal.class.php b/htdocs/comm/propal/class/propal.class.php
index 4d632a84c54..8d4c91f097d 100644
--- a/htdocs/comm/propal/class/propal.class.php
+++ b/htdocs/comm/propal/class/propal.class.php
@@ -496,17 +496,7 @@ class Propal extends CommonObject
             $this->line->date_start=$date_start;
             $this->line->date_end=$date_end;
 
-
-			// infos marge
-			if (!empty($fk_product) && empty($fk_fournprice) && empty($pa_ht)) {
-			    // by external module, take lowest buying price
-			    include_once DOL_DOCUMENT_ROOT.'/fourn/class/fournisseur.product.class.php';
-			    $productFournisseur = new ProductFournisseur($this->db);
-			    $productFournisseur->find_min_price_product_fournisseur($fk_product);
-			    $this->line->fk_fournprice = $productFournisseur->product_fourn_price_id;
-			} else {
-			    $this->line->fk_fournprice = $fk_fournprice;
-			}
+			$this->line->fk_fournprice = $fk_fournprice;
 			$this->line->pa_ht = $pa_ht;
 
             // Mise en option de la ligne
@@ -660,16 +650,7 @@ class Propal extends CommonObject
             $this->line->skip_update_total	= $skip_update_total;
             $this->line->fk_unit	= $fk_unit;
 
-            // infos marge
-            if (!empty($fk_product) && empty($fk_fournprice) && empty($pa_ht)) {
-                // by external module, take lowest buying price
-                include_once DOL_DOCUMENT_ROOT.'/fourn/class/fournisseur.product.class.php';
-			    $productFournisseur = new ProductFournisseur($this->db);
-			    $productFournisseur->find_min_price_product_fournisseur($fk_product);
-			    $this->line->fk_fournprice = $productFournisseur->product_fourn_price_id;
-			} else {
-			    $this->line->fk_fournprice = $fk_fournprice;
-			}
+			$this->line->fk_fournprice = $fk_fournprice;
             $this->line->pa_ht = $pa_ht;
 
             $this->line->date_start=$date_start;
@@ -3124,11 +3105,18 @@ class PropaleLigne  extends CommonObjectLine
 
         if (empty($this->pa_ht)) $this->pa_ht=0;
 
-        // si prix d'achat non renseigne et utilise pour calcul des marges alors prix achat = prix vente
-        if ($this->pa_ht == 0) {
-        	if ($this->subprice > 0 && (isset($conf->global->ForceBuyingPriceIfNull) && $conf->global->ForceBuyingPriceIfNull == 1))
-        		$this->pa_ht = $this->subprice * (1 - $this->remise_percent / 100);
-        }
+       // if buy price not defined, define buyprice as configured in margin admin
+		if ($this->pa_ht == 0) 
+		{
+			if (($result = $this->defineBuyPrice($this->subprice, $this->remise_percent, $this->fk_product)) < 0)
+			{
+				return $result;
+			}
+			else
+			{
+				$this->pa_ht = $result;
+			}
+		}
 
         // Check parameters
         if ($this->product_type < 0) return -1;
@@ -3296,10 +3284,17 @@ class PropaleLigne  extends CommonObjectLine
 
 		if (empty($this->pa_ht)) $this->pa_ht=0;
 
-		// si prix d'achat non renseigne et utilise pour calcul des marges alors prix achat = prix vente
-		if ($this->pa_ht == 0) {
-			if ($this->subprice > 0 && (isset($conf->global->ForceBuyingPriceIfNull) && $conf->global->ForceBuyingPriceIfNull == 1))
-				$this->pa_ht = $this->subprice * (1 - $this->remise_percent / 100);
+		// if buy price not defined, define buyprice as configured in margin admin
+		if ($this->pa_ht == 0) 
+		{
+			if (($result = $this->defineBuyPrice($this->subprice, $this->remise_percent, $this->fk_product)) < 0)
+			{
+				return $result;
+			}
+			else
+			{
+				$this->pa_ht = $result;
+			}
 		}
 
         $this->db->begin();
diff --git a/htdocs/commande/class/commande.class.php b/htdocs/commande/class/commande.class.php
index d43314a8816..e3926603f86 100644
--- a/htdocs/commande/class/commande.class.php
+++ b/htdocs/commande/class/commande.class.php
@@ -1281,16 +1281,7 @@ class Commande extends CommonOrder
             $this->line->date_start=$date_start;
             $this->line->date_end=$date_end;
 
-			// infos marge
-			if (!empty($fk_product) && empty($fk_fournprice) && empty($pa_ht)) {
-			    // by external module, take lowest buying price
-			    include_once DOL_DOCUMENT_ROOT.'/fourn/class/fournisseur.product.class.php';
-			    $productFournisseur = new ProductFournisseur($this->db);
-			    $productFournisseur->find_min_price_product_fournisseur($fk_product);
-			    $this->line->fk_fournprice = $productFournisseur->product_fourn_price_id;
-			} else {
-			    $this->line->fk_fournprice = $fk_fournprice;
-			}
+			$this->line->fk_fournprice = $fk_fournprice;
 			$this->line->pa_ht = $pa_ht;
 
             // TODO Ne plus utiliser
@@ -2509,16 +2500,7 @@ class Commande extends CommonOrder
             $this->line->skip_update_total=$skip_update_total;
 	        $this->line->fk_unit=$fk_unit;
 
-			// infos marge
-			if (!empty($fk_product) && empty($fk_fournprice) && empty($pa_ht)) {
-			    //by external module, take lowest buying price
-			    include_once DOL_DOCUMENT_ROOT.'/fourn/class/fournisseur.product.class.php';
-			    $productFournisseur = new ProductFournisseur($this->db);
-			    $productFournisseur->find_min_price_product_fournisseur($fk_product);
-			    $this->line->fk_fournprice = $productFournisseur->product_fourn_price_id;
-			} else {
-			    $this->line->fk_fournprice = $fk_fournprice;
-			}
+			$this->line->fk_fournprice = $fk_fournprice;
 			$this->line->pa_ht = $pa_ht;
 
             // TODO deprecated
@@ -3550,10 +3532,17 @@ class OrderLine extends CommonOrderLine
 
 		if (empty($this->pa_ht)) $this->pa_ht=0;
 
-		// si prix d'achat non renseigne et utilise pour calcul des marges alors prix achat = prix vente
-		if ($this->pa_ht == 0) {
-			if ($this->subprice > 0 && (isset($conf->global->ForceBuyingPriceIfNull) && $conf->global->ForceBuyingPriceIfNull == 1))
-				$this->pa_ht = $this->subprice * (1 - $this->remise_percent / 100);
+		// if buy price not defined, define buyprice as configured in margin admin
+		if ($this->pa_ht == 0) 
+		{
+			if (($result = $this->defineBuyPrice($this->subprice, $this->remise_percent, $this->fk_product)) < 0)
+			{
+				return $result;
+			}
+			else
+			{
+				$this->pa_ht = $result;
+			}
 		}
 
         // Check parameters
@@ -3677,10 +3666,17 @@ class OrderLine extends CommonOrderLine
 		if (empty($this->fk_parent_line)) $this->fk_parent_line=0;
 		if (empty($this->pa_ht)) $this->pa_ht=0;
 
-		// si prix d'achat non renseigné et utilisé pour calcul des marges alors prix achat = prix vente
-		if ($this->pa_ht == 0) {
-			if ($this->subprice > 0 && (isset($conf->global->ForceBuyingPriceIfNull) && $conf->global->ForceBuyingPriceIfNull == 1))
-				$this->pa_ht = $this->subprice * (1 - $this->remise_percent / 100);
+		// if buy price not defined, define buyprice as configured in margin admin
+		if ($this->pa_ht == 0) 
+		{
+			if (($result = $this->defineBuyPrice($this->subprice, $this->remise_percent, $this->fk_product)) < 0)
+			{
+				return $result;
+			}
+			else
+			{
+				$this->pa_ht = $result;
+			}
 		}
 
 		$this->db->begin();
diff --git a/htdocs/compta/facture/class/facture.class.php b/htdocs/compta/facture/class/facture.class.php
index bd3e2dac6f0..bc286cd2a59 100644
--- a/htdocs/compta/facture/class/facture.class.php
+++ b/htdocs/compta/facture/class/facture.class.php
@@ -2361,16 +2361,7 @@ class Facture extends CommonInvoice
 			$this->line->situation_percent  = $situation_percent;
 			$this->line->fk_unit				= $fk_unit;
 
-			// infos marge
-			if (!empty($fk_product) && empty($fk_fournprice) && empty($pa_ht)) {
-			    // POS or external module, take lowest buying price
-			    include_once DOL_DOCUMENT_ROOT.'/fourn/class/fournisseur.product.class.php';
-			    $productFournisseur = new ProductFournisseur($this->db);
-			    $productFournisseur->find_min_price_product_fournisseur($fk_product);
-			    $this->line->fk_fournprice = $productFournisseur->product_fourn_price_id;
-			} else {
-			    $this->line->fk_fournprice = $fk_fournprice;
-			}
+			$this->line->fk_fournprice = $fk_fournprice;
 			$this->line->pa_ht = $pa_ht;
 
 			if (is_array($array_options) && count($array_options)>0) {
@@ -3883,10 +3874,17 @@ class FactureLigne extends CommonInvoiceLine
 
 		if (empty($this->pa_ht)) $this->pa_ht=0;
 
-		// si prix d'achat non renseigne et utilise pour calcul des marges alors prix achat = prix vente
-		if ($this->pa_ht == 0) {
-			if ($this->subprice > 0 && (isset($conf->global->ForceBuyingPriceIfNull) && $conf->global->ForceBuyingPriceIfNull == 1))
-				$this->pa_ht = $this->subprice * (1 - $this->remise_percent / 100);
+		// if buy price not defined, define buyprice as configured in margin admin
+		if ($this->pa_ht == 0) 
+		{
+			if (($result = $this->defineBuyPrice($this->subprice, $this->remise_percent, $this->fk_product)) < 0)
+			{
+				return $result;
+			}
+			else
+			{
+				$this->pa_ht = $result;
+			}
 		}
 
 		// Check parameters
@@ -3906,14 +3904,6 @@ class FactureLigne extends CommonInvoiceLine
 			}
 		}
 
-		// POS or by external module, take lowest buying price
-		if (!empty($this->fk_product) && empty($this->fk_fournprice) && empty($this->pa_ht)) {
-		    include_once DOL_DOCUMENT_ROOT.'/fourn/class/fournisseur.product.class.php';
-		    $productFournisseur = new ProductFournisseur($this->db);
-		    $productFournisseur->find_min_price_product_fournisseur($this->fk_product);
-		    $this->fk_fournprice = $productFournisseur->product_fourn_price_id;
-		}
-
 		$this->db->begin();
 
 		// Insertion dans base de la ligne
@@ -4081,10 +4071,17 @@ class FactureLigne extends CommonInvoiceLine
 
 		if (empty($this->pa_ht)) $this->pa_ht=0;
 
-		// si prix d'achat non renseigne et utilise pour calcul des marges alors prix achat = prix vente
-		if ($this->pa_ht == 0) {
-			if ($this->subprice > 0 && (isset($conf->global->ForceBuyingPriceIfNull) && $conf->global->ForceBuyingPriceIfNull == 1))
-				$this->pa_ht = $this->subprice * (1 - $this->remise_percent / 100);
+		// if buy price not defined, define buyprice as configured in margin admin
+		if ($this->pa_ht == 0) 
+		{
+			if (($result = $this->defineBuyPrice($this->subprice, $this->remise_percent, $this->fk_product)) < 0)
+			{
+				return $result;
+			}
+			else
+			{
+				$this->pa_ht = $result;
+			}
 		}
 
 		$this->db->begin();
diff --git a/htdocs/contrat/class/contrat.class.php b/htdocs/contrat/class/contrat.class.php
index 1d2bd9f4181..e38bb254f79 100644
--- a/htdocs/contrat/class/contrat.class.php
+++ b/htdocs/contrat/class/contrat.class.php
@@ -1283,10 +1283,18 @@ class Contrat extends CommonObject
 
 		    if (empty($pa_ht)) $pa_ht=0;
 
-			// si prix d'achat non renseigne et utilise pour calcul des marges alors prix achat = prix vente
-			if ($pa_ht == 0) {
-				if ($pu_ht > 0 && (isset($conf->global->ForceBuyingPriceIfNull) && $conf->global->ForceBuyingPriceIfNull == 1))
-					$pa_ht = $pu_ht * (1 - $remise_percent / 100);
+			
+			// if buy price not defined, define buyprice as configured in margin admin
+			if ($this->pa_ht == 0) 
+			{
+				if (($result = $this->defineBuyPrice($pu_ht, $remise_percent, $fk_product)) < 0)
+				{
+					return $result;
+				}
+				else
+				{
+					$pa_ht = $result;
+				}
 			}
 
 			// Insertion dans la base
@@ -1456,10 +1464,17 @@ class Contrat extends CommonObject
 
 	    if (empty($pa_ht)) $pa_ht=0;
 
-		// si prix d'achat non renseigne et utilise pour calcul des marges alors prix achat = prix vente
-		if ($pa_ht == 0) {
-			if ($pu > 0 && (isset($conf->global->ForceBuyingPriceIfNull) && $conf->global->ForceBuyingPriceIfNull == 1))
-				$pa_ht = $pu * (1 - $remise_percent / 100);
+		// if buy price not defined, define buyprice as configured in margin admin
+		if ($this->pa_ht == 0) 
+		{
+			if (($result = $this->defineBuyPrice($pu_ht, $remise_percent)) < 0)
+			{
+				return $result;
+			}
+			else
+			{
+				$pa_ht = $result;
+			}
 		}
 
 		$sql = "UPDATE ".MAIN_DB_PREFIX."contratdet set description='".$this->db->escape($desc)."'";
@@ -2481,12 +2496,20 @@ class ContratLigne extends CommonObjectLine
 
 	    if (empty($this->pa_ht)) $this->pa_ht=0;
 
-		// si prix d'achat non renseigné et utilisé pour calcul des marges alors prix achat = prix vente
-		if ($this->pa_ht == 0) {
-			if ($this->subprice > 0 && (isset($conf->global->ForceBuyingPriceIfNull) && $conf->global->ForceBuyingPriceIfNull == 1))
-				$this->pa_ht = $this->subprice * (1 - $this->remise_percent / 100);
+		// if buy price not defined, define buyprice as configured in margin admin
+		if ($this->pa_ht == 0) 
+		{
+			if (($result = $this->defineBuyPrice($this->subprice, $this->remise_percent, $this->fk_product)) < 0)
+			{
+				return $result;
+			}
+			else
+			{
+				$this->pa_ht = $result;
+			}
 		}
 
+
 		$this->db->begin();
 
 		// Update request
diff --git a/htdocs/core/class/commonobject.class.php b/htdocs/core/class/commonobject.class.php
index 1439915ebdb..e87145b8443 100644
--- a/htdocs/core/class/commonobject.class.php
+++ b/htdocs/core/class/commonobject.class.php
@@ -4180,4 +4180,66 @@ abstract class CommonObject
 
 		return true;
 	}
+	
+	 /**
+	 * define buy price if not defined
+	 *	set buy price = sell price if ForceBuyingPriceIfNull configured,
+	 *	 else if calculation MARGIN_TYPE = 'pmp' and pmp is calculated, set pmp as buyprice
+	 *	 else set min buy price as buy price
+	 *	 
+	 * @param float		$unitPrice		 product unit price
+	 * @param float		$discountPercent line discount percent
+	 * @param int		$fk_product		 product id
+	 *
+	 * @return	float <0 if ko, buyprice if ok
+	 */
+	public function defineBuyPrice($unitPrice = 0, $discountPercent = 0, $fk_product = 0) 
+	{
+		global $conf;
+	
+		$buyPrice = 0;
+		
+		if (($unitPrice > 0) && (isset($conf->global->ForceBuyingPriceIfNull) && $conf->global->ForceBuyingPriceIfNull == 1))
+		{
+			$buyPrice = $unitPrice * (1 - $discountPercent / 100);
+		}
+		else
+		{
+			// Get PMP
+			if (! empty($fk_product))
+			{
+				if (isset($conf->global->MARGIN_TYPE) && $conf->global->MARGIN_TYPE == 'pmp')
+				{
+					require_once DOL_DOCUMENT_ROOT.'/product/class/product.class.php';
+					$product = new Product($this->db);
+					$result = $product->fetch($fk_product);
+					if ($result <= 0)
+					{
+						$this->error='ErrorProductIdDoesNotExists';
+						return -1;
+					}
+					if (($product->pmp > 0))
+					{
+						$buyPrice = $product->pmp;
+					}
+					// TODO add option to set PMP of product
+				}
+				else if (isset($conf->global->MARGIN_TYPE) && $conf->global->MARGIN_TYPE == '1')
+				{
+					require_once DOL_DOCUMENT_ROOT.'/fourn/class/fournisseur.product.class.php';
+					$productFournisseur = new ProductFournisseur($this->db);
+					if (($result = $productFournisseur->find_min_price_product_fournisseur($fk_product)) > 0)
+					{
+						$buyPrice = $productFournisseur->fourn_price;
+					}
+					else
+					{
+						$this->error = $productFournisseur->error;
+						return -1;
+					}
+				}
+			}
+		}
+		return $buyPrice;
+	}
 }
diff --git a/htdocs/langs/en_US/margins.lang b/htdocs/langs/en_US/margins.lang
index eb77ca9fe4c..9aeaf8d60e6 100644
--- a/htdocs/langs/en_US/margins.lang
+++ b/htdocs/langs/en_US/margins.lang
@@ -24,7 +24,7 @@ StartDate=Start date
 EndDate=End date
 Launch=Start
 ForceBuyingPriceIfNull=Force buying price if null
-ForceBuyingPriceIfNullDetails=if "ON", margin will be zero on line (buying price = selling price), otherwise ("OFF"), marge will be equal to selling price (buying price = 0)
+ForceBuyingPriceIfNullDetails=if "ON", margin will be zero on line (buying price = selling price), otherwise ("OFF"), marge will be equal to suggested default.
 MARGIN_METHODE_FOR_DISCOUNT=Margin method for global discounts
 UseDiscountAsProduct=As a product
 UseDiscountAsService=As a service