I claimed my parents as dependent for 2019 tax return. They are receiving SSA pension and are eligible for EIP/stimulus check. Since I had claimed them on my tax return, did I just make them ineligible for receiving the stimulus check? And if so, can I amend my tax to remove them as my dependents? AND in doing so, will they eventually receive the check after my return gets amended?
You parents are not eligible because someone could claim them as a dependent, even if you actually don't. The law says that people who could be claimed are not eligible. Even if you amended your return and did not claim them they would still not be eligible.
However, if they are independent when they file for 2020 next spring, they will get the check as a tax credit. Obviously they have to pay more than 50% of their living expenses before they can be considered independent. If you could still claim them for 2020 then they won't see any stimulus money.