I kept the records in the Numbers app that was pre-installed on my iPhone. I kept track of all expenses including for the reimbursement only companies. Those expenses offset the small profits from others. I only do restaurant and convenience store shops so most are reimbursement only or max $15 profit.
Fortunately, PayPal reporting is changing for 2025 to the old 1099 reporting rule of 200 transactions and over $20k. I certainly won’t exceed that unless they count using my PayPal debit card as a transaction. I’ll have to verify that those don’t count. Still can’t imagine I’ll be near $20k unless I start ebay selling again.