What happens when you accidentally put that you weren’t a dependent for the past year but you were?

[Mike9241]

you may get the stimulus payments which you are not entitled to.  whether other items on your return would be affected depends on their nature and your income 

[ColeenD3]

It is important that you give the IRS the correct information, stimulus aside. Your standard deduction may have been lower, based on your income and if you had an Education Credit, that would be affected.

You will need to amend your return.

First, make sure you really need to amend and that your 2020 return was accepted in TurboTax Online or paper-filed through the mail. You can't amend a return that hasn't been filed yet.

1. Sign in to TurboTax.
2. Scroll down to Your tax return & documents (you may need to select Show), select 2020 and then Amend (change) return.
   • If you only see the option to amend 2019 or earlier, it's because you can't amend an unfiled 2020 return. Instead, just select Pick up where you left off, make your changes, and disregard the rest of these instructions.
3. Select Amend using TurboTax Online.
4. Carefully follow the instructions. Don't worry if your refund changes to $0. This is normal on amended returns.
5. You can e-file your 2020 amended federal tax return, but most states require amendments to be printed and filed by mail.
6. If e-filing, you’ll review, sign and transmit your federal return. If not, we'll give you instructions to print and mail your amended return.

Three weeks after mailing your amended return, you can start tracking it at the IRS Where's My Amended Return? tracking tool.  Please allow at least 16 weeks for the IRS to process your amended return.

Processing times for amended state returns vary from state to state. If it's been more than 12 weeks since you mailed your amended state return, and you haven't heard anything, we suggest you contact your state tax agency.