If I got a new job in October 2020 but did not get paid until 2021, do I need to include that in my taxes?

[SweetieJean]

No, but why didn't they pay you until then?  Most states requires payroll to be made within shorter time periods.

[MinhT1]

As you are on a cash basis, income received in 2021 is only reportable on your 2021 tax return (next year) even if the payment was for work done in 2020.

[trynatax2019]

The project ended late December. Took a while for my payment to go through the system and there were some hiccups I had to sort out with HR to get my payment.

[ErnieS0]

The IRS taxes you in the year income is received, so as Tax Expert @MinhT1 the money should be taxed in 2021. Double-check with HR to make sure they are not going to issue a 2020 W-2 or 1099-NEC. 

They should not, but you said there were some hiccups so it's worth checking.