Legal requirements
What's necessary to meet legal requirements? I'm thinking about taxes, but there might be more to consider.

Kasisto will expect some existing receipt from another system, most likely printed. When a seller creates a payment request with Kasisto, they will be able to enter an associated receipt id. This could be via keyboard input, taking a picture of the receipt or scanning a barcode containing the receipt id.

Considering the seller can print a payment confirmation for the buyer and can export or print a transaction history for themselves, would this be sufficient to meet legal requirements?

If it's some specific issue, e.g. a certain country, please provide details.