- December 17 – Due date for calendar-year corporations to pay the last installment of 2012 estimated income tax.
- December 31 – Deadline to complete 2012 tax-free gifts of up to $13,000 per recipient.
- December 31 – Deadline for paying expenses you want to be able to deduct on your 2012 income tax return.
- December 31 – Deadline for taking 2012 required minimum distributions (RMDs).