If I want to claim ERC as an employer, I assume I have to amend 2020 and 2021 to remove the wages from Sch C?

Am I getting this right? It sounds like I can possibly claim the ERC credit for all the employee wages. So, if an employee made 15k in 2020, and 40k in 2021, I can claim 7.5k ERC in 2020 and 20k in 2021? But then I'd have to remove all those wages from my schedule C deduction, is that correct? 

If I remove those wages from schedule C, my taxes go up by 5k in 2020 and 16k in 2021. 

So, if I amend my tax returns, how soon do I have to owe the additional tax amounts? Can I wait the 20 weeks to receive my ERC before paying those additional taxes on the amended returns? 

Edit: Actually, I remember that my 2021 is on extension, so I don't even have to "amend it" technically. But what happens with my 2020 return?