How do you report hours that vary week to week? - 9 months and counting

I picked up part-time shifts as an IT help-desk technician and I am confused about how to report them. I do not usually post, so bear with me. Sometimes my paycheck is late by a week. Do you report when you earned it or when you were paid?

Keep everything in writing and save the confirmation numbers. It made the follow-up calls so much easier.