I received a 1099-K from my payment processor Shopify for my gross payment. I also received a 1099-NEC from a customer who's transaction was part of the 1099-K I got.

You should enter the 1099-NEC as the amount reported to you. When you report the amount on the 1099-K, you don't actually enter that form in TurboTax, just the amount  from which you will deduct the double reported income that is reported on the 1099-NEC form.

The IRS knows that the amount reported on the 1099-K form is often reported another the 1099 form, so it won't create a problem if you report a lesser amount for it.

Thanks so much, since I have cash receipts too which I report in the same section as the 1099-K. Couldn't I eventually just deduct the 1099-NEC out of the cash receipts and keep the 1099-K as is? Either way it comes out the same. Which way would be better or doesn't it matter?

Thanks

It is more important to report the 1099-NEC in full and adjust the 1099-K information to report the rest of your income.

The 1099-NEC may have withholding amounts and the IRS matches the filed 1099-NEC to your return in its review process.  There are a number of reasons the 1099-K may not match exactly so that form is less scrutinized.

Thanks, the IRS does not see each individual 1099-K on my tax return right? I list each one separate but when looking at my .pdf file of last years return, that info doesn't even show up, only the total amount of all income.

No, you do not actually enter your 1099-K on your return.  You enter it as cash or credit card receipts under the activity that caused you to receive the money.

The IRS does however, get a copy of each K-1 sent to you from the company issuing the K-1.