Reporting part-time earnings while on benefits - what worked for you?

I work some days through a staffing agency while still certifying. I have been trying to stay organised about it. Pay posts on a different day from when I work. Do you report when you earned it or when you were paid?

The claimant handbook has worked examples for part-time pay. Mine was clearer than the phone line.

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