Go to any Post Office location. Take cash, a debit card, or a traveler's check.Fill in the name of the payee. Fill out your money order using a black or blue pen and print clearly. Because money orders are prepaid, you'll need to pay for yours upfront. Western Union money orders offer a reliable, convenient alternative to cash or a check. Use them to give a gift, make a purchase, or even pay a bill. Safe, quick and easy electronic payment options available. If you mail your tax payment, make your check, money order or cashier's check payable to US Treasury. This page includes forms, fees, and instructions for all domestic business entities, foreign and domestic Registered Agents, and Washington Trademarks.