@Anitavanhoose
The details are still unclear on how all stimulus stuff will work out. You niece gets a $500 tax credit for claiming you as a dependent, but she does not get any additional stimulus $.
Since you are on SSDI, I assume you do not file a tax return. It's my understanding that because you get an SSA-1099 form for the SSDI, you will automatically get a stimulus payment late in April.
Even if you don't, you can file a 2020 tax return, in 2021 and get it then.
"In essence, the stimulus check acts as an advance of a person's 2020 income tax refund. This means when he prepares his 2020 income tax return, there will be a line to include the section 6428 credit. The credit on his 2020 return is subtracted by any amount received as a stimulus check in 2020. If the amount he received as a stimulus check is less than the credit he is due, the difference will be included as part of his 2020 refund. If he has been overpaid by receiving the stimulus check, however, he will not be required to return any excess amount".
