If you are staff member of an IO (not a consultant) and receive a 1099-NEC, you should enter it as ordinary income as if you had received a W2 form. (Note, the following probably doesn't apply if you are a consultant!):
You will not be entering any deductions (since your IO doesn't take them from your pay) on the W2 form in TurboTax, but make sure to continue through the TurboTax questions to the "unusual situations" page and check the box to show that you work for an international organization. You also need to continue through the questions which ask you how much of your income is taxable -- you only need to pay tax for the portion of the year when you were physically in the USA. If you never left the USA, then enter the full amount. If you were out of the US for 1/10th of the year, you would multiply the income shown on your 1099-NEC by .9 and enter that amount, which will likely result in a reduction in the self employed tax you owe. (Caution -- you are NOT actually self employed so should be careful not to try and deduct the sorts of expenses which you could deduct if you were self employed.) TurboTax will calculate your self-employed tax (which you have to pay because your employer did not take deductions for Social Security and Medicare) but will credit you with 50% of the amount you owe for the year.
