I feel like this might be Service Canada’s best kept secret. But maybe you already know about it.
https://validation-service-canada.canada.ca/en
Service Canada has a document upload portal that allows you to upload those EI Request for Payroll Information documents. You know then ones you get in the mail that say it was due yesterday and you have to mail it back to Quebec! LOL.
There are also other documents you can upload, but I mostly just use it for the EI requests.
Hopefully you find this tool helpful