Reporting part-time earnings while on benefits, pharmacy technician here

I picked up part-time shifts as a pharmacy technician and I am confused about how to report them. Any experience at all would help. Sometimes my paycheck is late by a week. Do you report when you earned it or when you were paid?

Thanks for writing this out. I went through something close to it 5 months ago, and it got easier once I kept a simple log of every call and form.