diff --git a/migration/360lts-release/oracle/826_IDEMPIERE-118.sql b/migration/360lts-release/oracle/826_IDEMPIERE-118.sql
new file mode 100644
index 0000000000..6c6ca7599c
--- /dev/null
+++ b/migration/360lts-release/oracle/826_IDEMPIERE-118.sql
@@ -0,0 +1,12 @@
+-- Mar 19, 2012 8:33:59 PM MYT
+-- IDEMPIERE-118 Average Costing: Negative Inventory
+UPDATE AD_Column SET ReadOnlyLogic=NULL,Updated=TO_DATE('2012-03-19 20:33:59','YYYY-MM-DD HH24:MI:SS'),UpdatedBy=100 WHERE AD_Column_ID=13455
+;
+
+UPDATE AD_System
+  SET LastMigrationScriptApplied='826_IDEMPIERE-118.sql'
+WHERE LastMigrationScriptApplied<'826_IDEMPIERE-118.sql'
+   OR LastMigrationScriptApplied IS NULL
+;
+
+
diff --git a/migration/360lts-release/postgresql/826_IDEMPIERE-118.sql b/migration/360lts-release/postgresql/826_IDEMPIERE-118.sql
new file mode 100644
index 0000000000..0585a803c5
--- /dev/null
+++ b/migration/360lts-release/postgresql/826_IDEMPIERE-118.sql
@@ -0,0 +1,10 @@
+-- Mar 19, 2012 8:33:59 PM MYT
+-- IDEMPIERE-118 Average Costing: Negative Inventory
+UPDATE AD_Column SET ReadOnlyLogic=NULL,Updated=TO_DATE('2012-03-19 20:33:59','YYYY-MM-DD HH24:MI:SS'),UpdatedBy=100 WHERE AD_Column_ID=13455
+;
+
+UPDATE AD_System
+  SET LastMigrationScriptApplied='826_IDEMPIERE-118.sql'
+WHERE LastMigrationScriptApplied<'826_IDEMPIERE-118.sql'
+   OR LastMigrationScriptApplied IS NULL
+;
diff --git a/org.adempiere.base/src/org/compiere/acct/DocManager.java b/org.adempiere.base/src/org/compiere/acct/DocManager.java
index 26c6801bab..76af3bfd98 100644
--- a/org.adempiere.base/src/org/compiere/acct/DocManager.java
+++ b/org.adempiere.base/src/org/compiere/acct/DocManager.java
@@ -19,6 +19,7 @@ package org.compiere.acct;
 import java.sql.PreparedStatement;
 import java.sql.ResultSet;
 import java.sql.SQLException;
+import java.sql.Savepoint;
 import java.util.ArrayList;
 import java.util.List;
 
@@ -282,7 +283,8 @@ public class DocManager {
 			localTrxName = Trx.createTrxName("Post");
 			trxName = localTrxName;
 		}
-
+		
+		Trx trx = Trx.get(trxName, true);
 		String error = null;
 		try
 		{
@@ -292,10 +294,20 @@ public class DocManager {
 				Doc doc = Doc.get (as, AD_Table_ID, rs, trxName);
 				if (doc != null)
 				{
+					Savepoint savepoint = trx.setSavepoint(null);
 					error = doc.post (force, repost);	//	repost
 					status = doc.getPostStatus();
 					if (error != null && error.trim().length() > 0)
+					{
+						trx.rollback(savepoint);
 						break;
+					}
+					else
+					{
+						try {
+							trx.releaseSavepoint(savepoint);
+						} catch (Exception e) {}
+					}
 				}
 				else
 				{
@@ -311,7 +323,6 @@ public class DocManager {
 				ValueNamePair dbError = CLogger.retrieveError();
 				// log.log(Level.SEVERE, "(doc not saved) ... rolling back");
 				if (localTrxName != null) {
-					Trx trx = Trx.get(localTrxName, false);
 					if (trx != null)
 						trx.rollback();
 				}
@@ -321,7 +332,6 @@ public class DocManager {
 					error = "SaveError";
 			}
 			if (localTrxName != null) {
-				Trx trx = Trx.get(localTrxName, false);
 				if (trx != null)
 					trx.commit();
 			}
@@ -329,7 +339,6 @@ public class DocManager {
 		catch (Exception e)
 		{
 			if (localTrxName != null) {
-				Trx trx = Trx.get(localTrxName, false);
 				if (trx != null)
 					trx.rollback();
 			}
@@ -342,7 +351,6 @@ public class DocManager {
 		{
 			if (localTrxName != null)
 			{
-				Trx trx = Trx.get(localTrxName, false);
 				if (trx != null)
 					trx.close();
 			}
diff --git a/org.adempiere.base/src/org/compiere/model/MCost.java b/org.adempiere.base/src/org/compiere/model/MCost.java
index 5c524ba763..e01ff10958 100644
--- a/org.adempiere.base/src/org/compiere/model/MCost.java
+++ b/org.adempiere.base/src/org/compiere/model/MCost.java
@@ -1441,6 +1441,15 @@ public class MCost extends X_M_Cost
 	 */
 	public void add (BigDecimal amt, BigDecimal qty)
 	{
+		MCostElement costElement = (MCostElement) getM_CostElement();
+		if (costElement.isAveragePO() || costElement.isAverageInvoice()) 
+		{
+			if (getCurrentQty().add(qty).signum() < 0)
+			{
+				throw new AverageCostingNegativeQtyException("Product(ID)="+getM_Product_ID()+", Current Qty="+getCurrentQty()+", Trx Qty="+qty
+						+ ", CostElement="+costElement.getName()+", Schema="+getC_AcctSchema().getName());
+			}
+		}
 		setCumulatedAmt(getCumulatedAmt().add(amt));
 		setCumulatedQty(getCumulatedQty().add(qty));
 		setCurrentQty(getCurrentQty().add(qty));
@@ -1462,7 +1471,8 @@ public class MCost extends X_M_Cost
 		
 		if (getCurrentQty().add(qty).signum() < 0)
 		{
-			throw new AverageCostingNegativeQtyException("Product(ID)="+getM_Product_ID()+", Current Qty="+getCurrentQty()+", Trx Qty="+qty);
+			throw new AverageCostingNegativeQtyException("Product(ID)="+getM_Product_ID()+", Current Qty="+getCurrentQty()+", Trx Qty="+qty
+					+", CostElement="+getM_CostElement().getName()+", Schema="+getC_AcctSchema().getName());
 		}
 		
 		BigDecimal oldSum = getCurrentCostPrice().multiply(getCurrentQty());
@@ -1616,6 +1626,17 @@ public class MCost extends X_M_Cost
 			if (getCumulatedQty().signum() != 0)
 				setCumulatedQty(Env.ZERO);
 		}
+		
+		//-ve current qty will break moving average costing
+		if ((ce.isAveragePO() || ce.isAverageInvoice()) && is_ValueChanged(COLUMNNAME_CurrentQty)) 
+		{
+			if (getCurrentQty().signum() < 0)
+			{
+				throw new AverageCostingNegativeQtyException("Product(ID)="+getM_Product_ID()+", Current Qty="+getCurrentQty()
+						+", CostElement="+getM_CostElement().getName()+", Schema="+getC_AcctSchema().getName());
+			}
+		}
+		
 		return true;
 	}	//	beforeSave
 
@@ -1630,6 +1651,20 @@ public class MCost extends X_M_Cost
 	}	//	beforeDelete
 
 
+	@Override
+	public void setCurrentQty(BigDecimal CurrentQty) {
+		MCostElement ce = (MCostElement)getM_CostElement();
+		if (ce.isAveragePO() || ce.isAverageInvoice()) 
+		{
+			if (CurrentQty.signum() < 0)
+			{
+				throw new AverageCostingNegativeQtyException("Product(ID)="+getM_Product_ID()+", Current Qty="+getCurrentQty()+", New Current Qty="+CurrentQty
+						+", CostElement="+ce.getName()+", Schema="+getC_AcctSchema().getName());
+			}
+		}
+		super.setCurrentQty(CurrentQty);
+	}
+
 	/**
 	 * 	Test
 	 *	@param args ignored