I filed my 2020 taxes have never received any economic impact payments. I do believe that I am eligible based off of the IRS checklist but I am not sure how to proceed.

When you prepared your 2020 tax return did you answer the questions in the Federal Review section about the recovery rebate credit?   Was there an amount on line 30 of your Form 1040?   If you did not receive the 1st and/or 2nd EIP payments you could get it as a credit on your 2020 return if you are eligible.   If you could be claimed as someone else's dependent you are not eligible, or if your income was too high you are not eligible.

If you somehow did not claim the credit on your 2020 return you can amend it to seek the recovery rebate credit.   Be aware that it takes the IRS at least six months to process an amended return, so do not expect quick results.

Select your tax year for amending instructions:

• 2020
• 2019
• 2018

The stimulus check is an advance on a credit you can receive on your 2020 tax return.  If something went wrong or you did not get the stimulus check in 2020, you can get it when you file your 2020 return in early 2021

The Recovery Rebate Credit will be found in the FEDERAL REVIEW section. ( you should see "Let's make sure you got the right stimulus amount”)  If you are eligible it will end up on line 30 of your 2020 Form 1040.

Make sure that you enter ALL of the stimulus money received for the 1st and 2nd stimulus for yourself, your spouse and your children.

https://www.irs.gov/newsroom/economic-impact-payment-information-center-topic-j-reconciling-on-your-2020-tax-return

There is no place to enter anything about the 3rd stimulus payment on a 2020 return.   If you did not get that one you can get the credit on your 2021 return if you are eligible.