I took a loan out through my 401K in 2019. I am still paying it back with interest but the interest I pay goes back to my 401K. do I need to report this on my 2020 taxes?

[DoninGA]

Loan payments you make on a 401(k) loan, including principle and interest, are not reported on a tax return.

[VolvoGirl]

No.  Only if you stop working there and/or don't pay it back.  Then it turns into a distribution.   You do report it if you get a 1099R for it.