What if I forget to attach the 8606?

[ZMO]

Hi,

I have already filed my tax this year with turbotax Desktop, but later I found I forget to report my non-deductible IRA contributions.

I heard I need to file a 8606 form for that. Should I just mail is separately, or I should file it together with a 1040X?

Does turbotax Desktop software support making this change?

[Mike9241]

File Form 8606 Separately: You can file Form 8606 by itself, without amending your tax returns.

use this link to find the address to use.

https://www.irs.gov/filing/where-to-file-addresses-for-taxpayers-and-tax-professionals-filing-form-1... 

[fanfare]

 You can file Form 8606 by itself, without amending your tax returns.

but lately IRS has been returning them to sender asking for Form 1040-X.

The proper way to file Form 8606 is attached to Form 1040-X.
Form 8606 can be mailed by itself only when you are otherwise not required to file a tax return.

Did you do a true backdoor contribution that is tax-free?
in that case Form 8606 will show a taxable amount of zero.
Do you have the correct taxable amount on Form 1040 Line 4b and did not take a deduction? (Schedule 1 Line 20)?
If that is all true then only Form 8606 has to be attached.
After you e-File,
get Form 1040-X from IRS website and mail it in with your 8606, which you can also get in fillable PDF.
Note: when you are not changing any dollar amounts on your 1040-X, you can leave all the lines 1-23 EMPTY.

Part III explanation: "didn't include Form 8606 with e-File".
You will have to mail it so this does not use up your one 1040-X e-File.
Done this way, you sign 1040-X, not 8606