diff --git a/htdocs/core/lib/functions2.lib.php b/htdocs/core/lib/functions2.lib.php
index ab41e5aaec7..66b64035c4d 100644
--- a/htdocs/core/lib/functions2.lib.php
+++ b/htdocs/core/lib/functions2.lib.php
@@ -607,7 +607,7 @@ function get_next_value($db,$mask,$table,$field,$where='',$objsoc='',$date='',$m
     	$maskraz=$yearoffsettype; // For backward compatibility
     else if ($yearoffsettype === '0' || (! empty($yearoffsettype) && ! is_numeric($yearoffsettype) && $conf->global->SOCIETE_FISCAL_MONTH_START > 1))
     	$maskraz = $conf->global->SOCIETE_FISCAL_MONTH_START;
-    //print "maskraz=".$maskraz;
+    //print "maskraz=".$maskraz;	// -1=no reset
 
     if ($maskraz > 0)    // A reset is required
     {
@@ -699,8 +699,8 @@ function get_next_value($db,$mask,$table,$field,$where='',$objsoc='',$date='',$m
             $sqlwhere.='(SUBSTRING('.$field.', '.(dol_strlen($reg[1])+1).', '.dol_strlen($reg[2]).") = '".$yearcomp."')";
         }
     }
-    //print "sqlwhere=".$sqlwhere."<br>\n";
-    //print "masktri=".$masktri." maskcounter=".$maskcounter." maskraz=".$maskraz." maskoffset=".$maskoffset." yearcomp=".$yearcomp."<br>\n";
+    //print "sqlwhere=".$sqlwhere." yearcomp=".$yearcomp."<br>\n";	// sqlwhere and yearcomp defined only if we ask a reset
+    //print "masktri=".$masktri." maskcounter=".$maskcounter." maskraz=".$maskraz." maskoffset=".$maskoffset."<br>\n";
 
     // Define $sqlstring
     $posnumstart=strpos($maskwithnocode,$maskcounter);	// Pos of counter in final string (from 0 to ...)
@@ -739,7 +739,10 @@ function get_next_value($db,$mask,$table,$field,$where='',$objsoc='',$date='',$m
         $counter = $obj->val;
     }
     else dol_print_error($db);
+
+    // Check if we must force counter to maskoffset
     if (empty($counter) || preg_match('/[^0-9]/i',$counter)) $counter=$maskoffset;
+    else if ($counter < $maskoffset && empty($conf->global->MAIN_NUMBERING_OFFSET_ONLY_FOR_FIRST)) $counter=$maskoffset;
 
     if ($mode == 'last')	// We found value for counter = last counter value. Now need to get corresponding ref of invoice.
     {
@@ -824,7 +827,7 @@ function get_next_value($db,$mask,$table,$field,$where='',$objsoc='',$date='',$m
             }
             else dol_print_error($db);
             if (empty($maskrefclient_counter) || preg_match('/[^0-9]/i',$maskrefclient_counter)) $maskrefclient_counter=$maskrefclient_maskoffset;
-            $maskrefclient_counter++;
+			$maskrefclient_counter++;
         }
 
         // Build numFinal
diff --git a/test/phpunit/NumberingModulesTest.php b/test/phpunit/NumberingModulesTest.php
index 82bb96dc0be..5e93e32fe22 100644
--- a/test/phpunit/NumberingModulesTest.php
+++ b/test/phpunit/NumberingModulesTest.php
@@ -147,7 +147,7 @@ class NumberingModulesTest extends PHPUnit_Framework_TestCase
 		$result=$localobject->is_erasable();
 		print __METHOD__." is_erasable=".$result."\n";
 		$this->assertEquals(1, $result);						// Can be deleted
-		
+
 		$localobject2=new Facture($this->savdb);
 		$localobject2->initAsSpecimen();
 		$localobject2->date=dol_mktime(12, 0, 0, 1, 1, 1916);	// we use following year for second invoice (there is no reset into mask)
@@ -166,7 +166,7 @@ class NumberingModulesTest extends PHPUnit_Framework_TestCase
 		$result=$localobject->is_erasable();
 		print __METHOD__." is_erasable=".$result."\n";
 		$this->assertEquals(0, $result);						// Case 1 can not be deleted (case 2 is more recent)
-		
+
 		// Now we try with a reset
 		$conf->global->FACTURE_MERCURE_MASK_CREDIT='{yyyy}-{0000@1}';
 		$conf->global->FACTURE_MERCURE_MASK_INVOICE='{yyyy}-{0000@1}';
@@ -194,7 +194,7 @@ class NumberingModulesTest extends PHPUnit_Framework_TestCase
 		$result=$localobject->is_erasable();
 		print __METHOD__." is_erasable=".$result."\n";
 		$this->assertEquals(1, $result);						// Can be deleted
-		
+
 		$localobject2=new Facture($this->savdb);
 		$localobject2->initAsSpecimen();
 		$localobject2->date=dol_mktime(12, 0, 0, 1, 1, 1921);	// we use following year for second invoice (and there is a reset required)
@@ -210,7 +210,11 @@ class NumberingModulesTest extends PHPUnit_Framework_TestCase
     	$result=$localobject->is_erasable();
     	print __METHOD__." is_erasable=".$result."\n";
     	$this->assertEquals(1, $result);						// Case 1 can be deleted (because there was a reset for case 2)
-    	 
+
+    	// Try an offset when an invoice already exists
+    	$conf->global->FACTURE_MERCURE_MASK_CREDIT='{yyyy}{mm}-{0000+9990}';
+    	$conf->global->FACTURE_MERCURE_MASK_INVOICE='{yyyy}{mm}-{0000+9990}';
+    	$result=$numbering->getNextValue($mysoc, $localobject2);
 
 		// Now we try with a different fiscal month (forced by mask)
     	$conf->global->FACTURE_MERCURE_MASK_CREDIT='{yyyy}{mm}-{0000@6}';