Taxpayer completes a service for Customer on December 28. Customer offers to pay by credit card in person the same day. Taxpayer regularly accepts credit card payments in Taxpayer's business, but Taxpayer refuses to accept payment and asks Customer to send a check instead. Customer mails the check on December 29, and Taxpayer receives the check January 2, Year 2. What are the tax consequences, assuming they are both on the cash method and that the payment represents a deductible expense for Customer?