You can fix this by going back to your T4 slip and answering “Yes” to the question “Will you claim employment expenses…” at the bottom of the page. You can get back to your T4 Slips by clicking on Find (magnifying glass) in the upper-right corner of your screen. In the Find window, type in “T4” and select “T4 Employment Income”. Click the “Go” button. Click “Edit” next to the T4 you want to change.

I have the same problem. I have already selected "Yes" to the last question about claiming employment expenses.

Please help!

I am having the exact same problem. I select 'yes' to the T4 income I am claiming employment expenses for due to COVID-19, but it send me back into the loop. It will not allow me to file via netfile because of this 'error;, but there is no 'error' and no way to fix. 

This is extremely frustrating because we paid for the tax return edition - and still no help!

I have the same problem, I have selected yes. Feels like a bug of the software, hoping it is being worked on.

Problem solved for me. I had put some numbers in the Detailed Method's fields, forgot to remove them and then choose to go with the Flat Method. If you leave numbers in Detailed, but file with Flat, it will generate the error until all fields in Detailed are set to 0 or cleared.

Hope it helps some of you!

Thank you!  This resolved the problem for me as well. 🙂

Perfect!  Man, that was frustrating... but rewarding to finally fix!

this solution does not work! and it is very frustrating

There is still no solution that works for this problem. I have been trying to file my taxes for two weeks. Extremely frustrated.