What is Bad RequestYour browser sent a request that this server could not understand.Size of a request header field exceeds server limit?

Hello there, Oksana. I'll share details about the error you're getting and troubleshooting steps you can use to resolve it.

The Bad Request error you encounter is caused by having a large Cookie that results in the request header field exceeding the limit set for the web server. Since you already clear your cache and does not work, I also recommend clearing "All site data".

On the other hand, you can also access your QuickBooks Online (QBO) account via incognito mode to verify if this issue is related to your web browser. Below are the shortcut keys you can use:

• Google Chrome: press Ctrl + Shift + N
• Mozilla Firefox: press Ctrl + Shift + P
• Microsoft Edge: press Ctrl + Shift + N
• Safari: press Command + Shift +N

Once signed in, run a payroll report again and check if you can still see the error. If the same thing happens, you can use another supported browser or device. Might be that the current one you're using has a temporary issue with the program. 

Please know that the Community is always open and feel free to post your QuickBooks concerns here. Have a good one.