Final answer:
A supplier will send a Debit Note to a customer to indicate an undercharged invoice amount, requesting the correct additional payment.
Step-by-step explanation:
When a supplier realizes that an invoice they sent to a customer was undercast, which means it charged less than it should have, the supplier will send a Debit Note to the customer. A debit note is a document issued by the supplier to the customer notifying them of the undercharge and requesting additional payment for the correct amount. This is different from an invoice, which is a bill for goods or services rendered, or a payment voucher, which is proof of a payment made. A cheque could be how the customer pays the difference, but it is not what the supplier would send to indicate the undercharged amount.