[working at home due to COVID-19 - Temporary flat rate method]

Had the same issue and I've reported it as well.

Wish I had seen your post.

Hope you realize there are 52 week-ends, 9 public holidays, and PTO days.

[Work at home expenses line 22900]

It seems to be a bug in calculating Other employment expenses line 22900.

Two weeks ago, I logged in and started to prepare my taxes. I did not have all the tax slips, I did not really want to fill my taxes, I just wanted to see how much I'm going to get in refund (approximately). There's a new feature "Download from CRA your prior tax information". I used it and it seemed OK, everything according to my expectations.

Today, after getting all tax slips I logged in again, this time,  to fill my taxes. I've been asked again to download my prior tax information from CRA.

Okay! I have no problem with that. But, after the second download I noticed that I got 2 records for claiming work at home expenses, flat rate, due to COVID-19.

If I fill them both, I get double W@H expenses, $884 in my case, greater than the maximum of $500 allowed by CRA.

The workaround is to fill only 1 record to get the correct calculation.

If you fill both of them the calculation is wrong and most probably the filling is going to be rejected by CRA.