What payment reference should I ask my customer to include?

Give the customer your invoice number or another clear reference that identifies the payment. If the receiving instructions specify a particular reference, follow those instructions exactly and explain where the payer should enter it.

Put the reference beside the bank details in your payment instructions, rather than expecting the payer to find it elsewhere on the invoice. Ask them to check that it appears in the final transfer record.

Do not use the reference to replace the beneficiary account number or routing code. It helps identify the payment but does not route funds to the correct account by itself. Keep the invoice and the customer's receipt together so any query can be matched to the right collection.