The Cash Sales option does two things:

1. it creates an invoice (and adjusts the stock down if a Stock Item is included);
2. it creates a payment receipt.

So this option can be used any time that any customer pays immediately on presentation of the invoice, and whatever the method of payment.

You could raise a normal invoice, and then process the payment separately, so the Cash Sale option is really just a short cut to save you time.

You can also accept the default Anon/ Cash Sales customer account for both the invoice and payment to be posted to (so this account should always have a zero balance as the payment balances off the invoice), or you can select a specific customer account where you want to keep a record of the sale to that customer, in which case both the invoice and payment will be posted to that customer’s account.