2019 taxes i was filed as an adult dependant for the first tims in 15 years. I have every other year filed my own taxes. Will I qualify for a stimulus check or a $1200 refundable credit on my 2020 taxes? In 2018 i filed my own taxes and could not be claimed as a dependent. I don't understand why I would be excluded since they have said they would go by a person's 2018 return if they have not yet filed for 2019. People who made too much money in 2019 and have not yet filed for 2019 are using their AGI on their 2018 returns to qualify.
First off, you are correct, the IRS will use 2019 data first, and then 2018 data if that is not available. However, you were put down on someone else's return for 2019 so you have technically filed. Therefore they will not look at 2018 and you will not get the stimulus check in April 2020 (the IRS might still send it to you if they do decide to look at 2018, but I doubt they would bother).
The person claiming you for 2019 will also not get the $500 for dependents since you are not a child under 17 years of age.
The only for sure way you will get the stimulus check is if you file independently for 2020 and no one is able to claim you as a dependent. Note that it does not depend on whether you get claimed or not. If someone could claim you, you are not eligible for the stimulus, even if they don't actually claim you.
there shall be allowed as a credit against the tax imposed by subtitle A for the first taxable year beginning in 2020
So, assuming you will meet the requirements for 2020, you'll just get the credit after you file your taxes in 2021.