I took a 401k withdrawal for a down payment for a home. I know the amount is taxable (I'm under 59). But a portion should be exempt from penalty. How do I log that?

Oh no.   You misunderstood.   There is no exemption from the early withdrawal penalty for money you took out of a 401k for a down payment.   That exception is only for a withdrawal from a traditional IRA for a down payment.   You are going to be subject to the 10% penalty and the ordinary tax.   Enter your 1099R on your tax return:

To enter your retirement income, Go to  Federal> Wages and Income>Retirement Plans and Social Security>IRA  401 k) Pension Plan Withdrawals to enter your 1099R.

Sorry. IRAs and 401(k)s are controlled by different sections of the tax law and have different rules, even though they have broadly similar purposes.  The exception to the 10% penalty for a first time home buyer applies to an IRA but not a 401(k). If you are within 60 days of the withdrawal, you could re-deposit the money into the 401(k), then do a partial rollover of the 401(k) money to an IRA and withdraw it from the IRA. But taking the money directly from the 401(k) is not exempt from the 10% early withdrawal penalty.

In 2022, can I do a partial rollover from my 401k into a IRA and then withdraw those funds for a first time home downpayment without incurring the 10% early withdrawal penalty?

@tabbott14 

Yes.  That’s the way you can use 401(k) funds for a “first time” home purchase and avoid the penalty, you have to do a rollover first.  Note the withdrawal from the IRA will still be subject to regular income tax, and the penalty exemption only applies to the first $10,000.   

Yes!  You can avoid the 10% early withdrawal penalty if the funds come from an IRA, but not from a 401K. 

Exception to 10% Additional Tax   You will see a YES in the IRA column for ''qualified first-time homebuyers, up to $10,000''    @tabbott14

Thank you!

If you are still working for the company providing the 401(k) plan, you'll need to check with the plan to see if any in-service distribution is permitted.  If not, you won't be able to do a rollover from the 401(k).  If you do perform a rollover from the 401(k), be sure to do it as a direct rollover to avoid otherwise mandatory tax withholding on the distribution from the 401(k).