Can someone help me with how to file a 1040x, when I did not originally file my taxes through TurboTax?

[VolvoGirl]

Ideally you should go back to who did it and they should amend it for free if it was their error.

To amend a return you did somewhere else or you don't have the original.tax file,  you would first have to fill out Turbo Tax like you are doing the original return and pay for it.  You have to recreate the actual wrong original return.  Then when it matches each line that you really filed you have to tell Turbo Tax you will mail it so it thinks it was filed.  Then you can amend it.

For the current year you can use the online version by first recreating the original return exactly as filed.  Then pay the fees and say to mail it and print it out so it think you filed it.  Then when it matches every line you can amend.

How to Amend this year

https://ttlc.intuit.com/turbotax-support/en-us/help-article/tax-return/amend-federal-tax-return-curr...

Or you can buy the Desktop CD/Download program here, https://turbotax.intuit.com/personal-taxes/cd-download/

To amend a prior year return you have to buy the Desktop program here.  They only sell the last 3 years.

TurboTax 2021 Prior Year Tax Prep - File Past Years' Taxes

You will have to print and mail the amended return.  You can only efile it from the same account the original was Accepted.

[fanfare]

The simplest way to amend is by hand.

You must have a copy of the original tax return you want to update (or a transcript).

Prepare your correct tax return (using TurboTax for example, or other means*) and print it.
Then lay the paper printouts of both returns (correct and original) side-by-side.
You now have all the information needed to prepare Form 1040-X by hand.
It's pretty straight-forward.

The blank form in fillable PDF format and its instructions are available at www.irs.gov.
Refer to the Instructions for what is to be attached to Form 1040-X.

That is - only forms that are new or changed due to your amendment.
You must find these by visual inspection, TurboTax won't break them out for you even when it is working.

Do not include your old 1040 nor your revised 1040 because the Form 1040-X reflects any changes there and becomes your new tax return.
Mail to the address shown in the Instructions.

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* There are other tax prep sites on the internet that will do your return again (federal) for no charge.

@Ashley-unger84