That doesn't make sense. Are you doing the amended return now? You have to send a check with the amended return. Do you mean a tax due you paid with the ORIGINAL return?
On the amended 1040X, Line 18 should be your original refund amount and line 22 should be your additional refund. If you paid on your original return it will be on line 16. If there is an amount owed with the amendment, it will be on line 20.
