Quicken Home & Business !!!!!
You can keep track of everything in your life, including mystery shopping
I enter my forthcoming scheduled shops as upcoming "Invoice Reminders."
Once I complete a shop, I enter the invoice with a payment due date so I know when I will get paid.
If I have any reimbursable expenses, I mark them as "reimbursable" in my various account registers when I enter the transaction.
You can attach files to any transaction in Quicken, so I upload copies of any receipts to the relevant transactions. And, I attach PDFs of my shop reports to most of my shop invoices.
Also, Quicken tracks mileage, and allows you to attach mileage records to specific jobs.
Reports can be run for just about anything you want.
I have found Quicken to be a flawless way to keep on top of my mystery shopping business. And, it is properly connected to the rest of my life. Taxes are a cinch at the end of the year because everything is already properly documented.
It's well worth the investment.