Does anyone know the fourm to fill out to unmark myself as a dependent? Its a 10-90x or something

[xmasbaby0]

You amend a tax return by preparing a Form 1040X.  But if you are hoping to amend your 2019 return to get stimulus money don't bother unless you have some other mistakes to fix on the return.  It is taking the IRS about six months or longer to process an amended  return.    If you cannot be claimed as anyone else's dependent for 2020 you can get the stimulus money on your 2020 return.

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 this year, you can get it when you file your 2020 return in early 2021—if you are eligible.It will end up on line 30 of your 2020 Form 1040.

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

https://www.irs.gov/coronavirus/coronavirus-tax-relief-and-economic-impact-payments-for-individuals-...

[NCperson]

@pleonard82 - are you asking because of the stimulus? 

if someone CAN claim you as a dependent (whether they actually do is immaterial), you are NOT eligible for the stimulus

there is no need to adjust the 2019 tax return as the stimulus is really based on your 2020 tax return.  Just fill it out properly and if a stimulus payment is due you, it will appear on Line 30 of Form 1040.