Does marking "Someone can claim me as a dependent" mean that they *DID* claim me or just that they could?
I am filing jointly with my spouse, and marked that someone can claim me as dependent, but they didn't. Should I go back and change that before I turn it in?
Yes, please change your selection before you will submit it. If you file Married Filing Jointly you cannot be anyone's dependent for tax purposes. And if you received stimulus payment as a dependent in 2020 or you didn't receive it at all, don't forget to claim your Recovery Rebate credit to adjust an amount of the stimulus payment. You're eligible for the full credit if you file your 2020 tax return as independent taxpayer.
