A credit memo reduces what a customer owes without paying cash. Apply it to an invoice so the open balance falls. A refund receipt records money paid back to a customer for a returned or canceled paid sale. Both reverse the relevant revenue and any related sales tax; neither belongs in an ordinary operating expense account.
A sales receipt records a sale paid immediately. It combines the earned sale and the receipt into one form. Choose the bank account or Undeposited Funds according to where the money actually goes. Keep customer advances separate: a payment received before performance creates a liability rather than immediate earned revenue. The right form preserves the customer history as well as the ledger effect.