Reporting part-time earnings while on benefits, administrative assistant here

I picked up part-time shifts as an administrative assistant and I am confused about how to report them. Any experience at all would help. The form asks for gross earnings, which I do not see until later. 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.

Report honestly and keep your stubs. An honest small error is much easier to fix than a missing report.