[jedberg]

Every expense system I've ever dealt with allowed me to submit my CC bill as proof.

[dheera]

Some places want it itemized. Also if you use cash you don't have a CC bill. Back when I was a student I had to often buy things for student events with several hundred dollars in cash because the CC company wouldn't give me a higher credit line at the time. I didn't want to use a debit card, that's risky.

[jedberg]

Then you’re back to the original problem of having to perfectly remember what you bought and for what price, otherwise you’re committing fraud.

[dheera]

That's easy, because the prices might still be physically listed somewhere if it's a store, or you might still have the Craigslist email thread, or whatever.

If you simply lost or don't have a receipt and it's done in good faith I don't think it should be considered fraud.