Reporting part-time earnings while on benefits after 14 years as a teaching assistant

I picked up part-time shifts as a teaching assistant and I am confused about how to report them. Pay posts on a different day from when I work. Do you report when you earned it or when you were paid?

Keep everything in writing and save the confirmation numbers. It saved me later.

I estimated and then checked my pay stub. When there was a small difference I wrote to the agency to correct it.