Tax Year Prior to 2020: I recieved another w-2 and a 1099R after I filed

[Daahved]

Will I need to amend my return my w-2 was only 100 taxable and I didn’t know I was receiving a 1099R

[KarenL]

You should amend.  The IRS will also receive copies of that W-2 (although minimal) and the 1099-R, and will send you a notice to amend or accept the additional penalties and interest for underpayment if any more taxes are owed.   When the form to amend is available (Form 1040X) the instructions at this link will be updated.  See How to Amend. 

[Daahved]

Okay and what if I don’t owe anything?

[KarenL]

If you don't owe anything, you won't have underpayment penalties or interest, but you will likely still get a letter from the IRS with them requesting you amend or adjusting on your behalf. If taxes were withheld from your 1099-R, you would want to amend to see if you can get some of that refunded as well, if you think you won't owe more.