TurboTax didn't prompt me to file for the Nebraska Property Tax Incentive Act Credit using Form PTC. Can I file for that credit using an amended NE tax return for 2021?

Currently, Nebraska does not allow online filing of amended returns. You can prepare it in TurboTax, but it will have to be mailed in. To prepare it in TurboTax, log into TurboTax, then scroll down to Your tax returns and documents and click Amend (change) return then Amend using TurboTax Online.

You may need to go through some screens to go through your federal return, assuming you are not making any changes to that. It will then ask if you'd like to amend your state return. Once you are in the Nebraska section, you may add Form PTC which is necessary for claiming the property tax credit by going through the TurboTax interview until you come to the Any Nebraska Credits? screen. Select Property Owned by an Individual Tax Credit. Enter the information regarding your school district property taxes paid on the next screen. The credit is for 25.3% of the school district property taxes paid. 

I followed the directions in your response, used TurboTax to prepare my 2021 Amended Nebraska Tax Return. I chose to print and mail the return. I got an extra $499 tax credit which made the effort worthwhile. Thanks.