Mr. RJ owns a consulting firm that uses a calendar year and the cash method. In November, Mr. RJ billed a client $3,500 for services performed in September. After waiting several weeks, he called the client to remind her of the bill. The embarrassed client promised to telephone Mr. RJ as soon as she prepared a check for $3,500. Mr. RJ left his business office on December 23 and didn't return until January 2. A message on his answering machine said that he could pick up his check from the client's receptionist. The message was dated December 30.
Identify the tax issue or issues suggested by the following situations, and state each issue in the form of a question.