In certain jurisdictions such as Singapore, sole proprietorships must be registered. In these jurisdictions, can a private individual issue receipts?
Perhaps a more specific legal question is: where does the authority to issue receipts come from? Does it rest exclusively with the recipient? If governmental authorities are permitted, by law, to regulate (1) the form and substance of receipts, (2) who is authorized to issue receipts - to what extent may they do so?
All this is assuming the individual makes a sufficiently low turnover that we can ignore VAT/GST.