How many stamps do you need to mail your federal tax return?

There are several factors that can determine the number of stamps that will be needed to mail a federal tax return. The first of those factors is the country for which the tax return is being filed. Each country has their own postage rates so that is an important consideration. Another factor would be how much paperwork is involved with one's specific tax return. The more paper in the package the heavier it will be and the more stamps it will require to mail.