If SSI or SSDI is your only income, then you owe not tax, are not required to file and there would be no tax benefit in doing so. To get the Child Tax Credit you have to owe tax. To get the Additional Child Tax Credit, you have to have earned income.
If you state has a non-refundable renters credit, that can only be used to off set state tax. If you owe no tax, there is no credit.
