I have a North Carolina K-1 showing an amount of withheld tax on line 9. How do I get this to show up on Form D-400 line 21c as expected?

This cannot be automatically listed on the form itself or is there a K-1 entry for you to make. To report the backup withholding, perform the following steps.

1. Click on Federal.
2. Select Deductions and Credits.
3. Look for Estimates and Other Taxes paid on the list.
4. Click Start or Review to the right of Income Taxes Paid.
5. Scroll down to Other Income Taxes Paid.
6. Find Withholding not already entered on a W-2 or 1099, click Start or Edit to the right.
7. Under State Withholding, select the state and enter the amount to the right.

This will actually appear in Line 20A on your North Carolina D400 return.  The slight difference will not jeopardize the reporting in your return and you will receive full credit for the payment.

you would have to add a NC return which should allow you to complete a NC k-1 where the tax withheld can be reported. entry would be made when you get to that state section. 

That sort of works. However, I know from past years' experience North Carolina will not recognize the payments if it the amount is not entered on the right line. After having to file amended returns to move the amount paid from 21a to 21c, I learned to force it in (the method varies by year) and then print the return, white out the wrong line, and write in the amount on line 21c. Doesn't seem like it should be this hard. It's been an issue for years and the information is entered elsewhere in TurboTax. 

A workaround that puts the value on a seemingly equivalent but not officially correct line does not seem like a safe solution. This seems like a bug in TurboTax to me.

Actual Fix: Line 21c is populated by entering information in Federal form K-1, box 13, code = W Other deductions.  You will be prompted to enter the ID = NC (state abbrv.) and amount. This will flow through to the NC state form D400, line 21c.

Entering the amount as a contribution to line 13W of the Federal K-1 would be a reasonable approach except that the amount was NOT included in that line. It only showed up on the North Carolina K-1.