What type of transaction increases the amount owed to a vendor?

In the context of accounts payable, the type of transaction that increases the amount owed to a vendor is an invoice. When a business receives an invoice from a vendor, it signifies that the vendor has provided goods or services, creating an obligation for the business to pay. This transaction reflects the company's liability on its balance sheet, as it recognizes the amount that needs to be settled in the future.

In contrast, a credit memo typically reduces the amount owed to a vendor. It is issued by a vendor to recognize a return of goods or a reduction in the amount billed. A refund is a transaction where money is returned to the business, also resulting in a decrease in the amount owed. Payment signifies a decrease in liability as it involves settling an amount that is already owed. Thus, the invoice is the correct choice, as it is the document that formally records an increase in the payable balance.