They might catch it, in which case they will send you a letter with what they think your refund or tax due should be.
You will have the option of agreeing or not. If not, you'll need to send back correspondence. If you agree, you just accept the refund or tax bill they send you.
If the IRS does not catch the error, be sure to file an amended return as soon as the original has processed.
If you will owe tax, make sure that tax gets paid by April 15th, 2021.