Your third stimulus check cannot be taken or reduced if you owe back taxes. It is also protected from federal and state debts, such as past-due child support. The rules are slightly different when claiming previous stimulus checks as the Recovery Rebate Credit.

None of the three stimulus checks (or Recovery Rebate Credits) are considered income, and therefore aren’t taxable. They won’t reduce your refund or increase what you owe when you file your taxes this year, or next. They also won’t affect your eligibility for any federal government assistance or benefits.

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What You Need to Know About Your 2020 Stimulus Check ...

Third Economic Impact Payment | Internal Revenue Service

But will it be taken out of the 2020 taxes that I owe to the federal government? Not back taxes. For instance, I was able to put in that I never received the second ($600) stimulus check, but not the third ($1400) even though I never received it. So that $600 was deducted from what I owe this year. Can I do the same with the $1400 because I don’t see a place to do so. 

No, the $1,400 stimulus check will be sent to you, you can't use it to reduce your income tax.