Karen is a fitness consultant and personal trainer. She charges her clients $2,000, payable in advance, for a month-long diet and exercise regimen designed to ensure the loss of a pre-determined amount of weight. Karen promises to refund the $2,000 fee to anyone who follows the diet and exercise regimen but fails to lose the specified amount of weight. Karen estimates that she refunds about five percent of the fees on this basis. At the end of December she holds $20,000 in fees from clients whose month-long regimens end in January. When must Karen report these fees?