type of envelope for returns that are mailed

[arqchicago]

Hi, I have to mail my tax return. Can I use a large 12x9 to send my return and the forms? I have several forms to include so it is a stack of papers. If yes, is it ok to send stay flat envelopes? 

[bosso3 · Accepted solution]

I have used 9x12 manilla envelopes for years.

I always mail it registered with a return receipt, to ensure it was received by the IRS or state.  I file the returned receipt with my copies of my return and forms.

[arqchicago]

Thanks! this is very helpful.

[fanfare]

Use any envelope the Post Office will accept.

Be sure to ask for correct postage.

[arqchicago]

thank you!