I just filed my taxes, which included my LLC. I now realize there was no spot for me to add in the quarterly federal tax payments I made in 2020. What do I do?

[JeffreyR77]

When you make your quarterly Federal tax payments, if they are made under your social security number and are posted for tax year 2020, the IRS should automatically adjust your account.  You can expect to receive a Letter from the IRS advising you that there are estimated payments on your account that need to be verified so they can issue a refund or apply them to your tax return.  

You can also amend your tax return in TurboTax online. Log in to your account, open the tax return you already filed, and click on the link to amend your return.  You can add the estimated federal tax payments in Deductions and Credits, Estimated Tax Payments, Federal estimated taxes for 2020 (Form 1040ES).

[Mike9241]

nothing for now. the IRS should catch that you made the payments. however, you now have to determine whether you owe or are getting a refund.  a refund presents no issues but you have to pay any balance due by 4/15/2020.

to make sure the IRS has a record of your estimates

https://www.irs.gov/individuals/transcript-types-and-ways-to-order-them 

you want th account transcript for 2020. 

[BillM223]

In the future, you will want to do a Search for estimated tax payments and click on the jump-to link (Mac user must find estimated tax payments in the Topics List).

After the jump you will be able to enter federal, state, and local estimated tax payments that you made during the year.

Also note that without the estimated tax payments having been entered, TurboTax may calculate a penalty for the underpayment of estimated taxes.

It's possible that the IRS will notice that you paid enough estimated taxes to prevent any penalty and send you a letter. What I would do is get the transcript periodically as Mike said to see if your account had the underpayment penalty reduced or removed. 

Eventually, if nothing happens, you may want to file an amended return, to get the underpayment penalty (if any) refunded.