Date , Target, Company, Reimbursement, Fee, Paid, Pay Date/Method, Outstanding, Note
Those are my columns. Target is just the store/restaurant/etc, and if there's a specific person, I'll put that in. I use the formulas to add up the columns for reimbursement, fee, paid, and outstanding so I can easily see what I've made, and what is still to come in. Reimbursement/Fee is what I should get back, and then paid is what I do get paid. Note is for if there's an issue with payment and I have to contact, I note the date/method of contact (ie Email sent on 2/8).
If I need to, I can sort the columns. So, for example, I can sort all the MSC companies alphabetically or see the last time I shopped a particular location or whatever. I also have an unnamed "blank" column next to date, where I put in if there's a specific time I need to shop during/after/etc, or if I'm doing a lot of shops in a day, so I know what time I need to do them (usually that doesn't matter too much since I don't do it full time).