Year-End Tax Moves Worth Making Before December 31

Most tax planning that actually changes what you owe has to happen inside the calendar year the income was earned — by the time a return is being prepared the following spring, the facts are already set, and preparation becomes documentation instead of strategy. December is the last real window each year to act on the handful of decisions that still have room to move the number.

Equipment and vehicle purchases are the most visible example. Section 179 and bonus depreciation both require the asset to be placed in service by year-end to count for that tax year — not ordered, not invoiced, but actually in use. A purchase decided on in early January instead of late December pushes an entire year's worth of deduction into the following year's return, which matters if this year's income was the year that needed the offset.

Retirement contributions have their own, separate deadlines that are easy to miss because they don't all match the calendar year. Employee deferrals into a Solo 401(k) generally have to be elected and, for many plan types, deposited by December 31, while employer profit-sharing contributions and SEP-IRA contributions can typically be made up until the tax filing deadline, including extensions. Knowing which contribution type has which deadline is exactly the kind of detail that gets missed without checking.

Income and expense timing is the other lever worth reviewing before year-end — deciding whether to accelerate a deductible expense into the current year or defer invoicing income into the next one, depending on which year's marginal rate and income level actually benefits from the shift. This only works with a real, current picture of the year's income, which is exactly why it has to happen in December, with real numbers, not as a guess made from memory.

None of these moves work retroactively once the calendar flips. That's the reason we run a year-end planning conversation with clients every December specifically — not a generic checklist, but a review of that client's actual numbers against the specific deadlines that are about to close for the year.