How much is to mail a federal tax return?

Assuming you mail in a regular-sized envelope, it is 42 cents up to 1 ounce.

59 cents up to two ounces, 76 cents up to 3 ounces and 93 cents up to 3.5 ounces.

An envelope plus about 5 or 6 pieces of 8.5 x 11 paper weighs one ounce.

The prices above are accurate if you are reading this before May 11, 2009.