Do you mean the 1040ES vouchers so that you can send in quarterly estimated payments to avoid an underpayment penalty at tax time next year? Not sure why you think those are supposed to fit an "IRS provided window envelope." If you need appropriate envelopes--you can purchase envelopes from many retail stores and write the address on the envelope yourself.
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
