December deadlines
These must happen by December 31:
- 401(k) elective deferrals (paycheck-funded by 12/31)
- Roth conversions (can't be unwound after year-end)
- Tax-loss harvesting in taxable accounts
- Charitable gifts (cash, stock, or qualified charitable distributions)
- RMDs from inherited and retirement accounts
- Section 179 equipment purchases (must be placed in service)
Pushed to April
IRA contributions, HSA contributions, SEP and Solo 401(k) employer contributions can all be made until the tax filing deadline (with extension) for the prior year. That split is the planning skeleton: December is for moves locked to the calendar year, spring is for contributions that look backward. Knowing which list an idea belongs to prevents both missed deadlines and unnecessary December panic.
Bunching deductions
With a high standard deduction, moderate itemized deductions do nothing in any single year. Bunching fixes that: concentrate two years of charitable giving into one year (a donor-advised fund makes this clean), pair it with a year of high medical costs or a property tax payment timed right, itemize that year, then take the standard deduction the next. Same total giving, meaningfully lower total tax across the two years.
Income timing
Cash-basis business owners can nudge income across the year line: invoice in January instead of December to defer, or accelerate collections into December when this year's bracket is unusually low. Employees have less room but not none, with bonus timing, equity exercises, and Roth conversion sizing all steerable. The direction depends entirely on which year's rate is higher, which is why the projection comes before the moves.
Don't let the tax tail wag the dog
Every December someone buys equipment they don't need to 'get the deduction,' spending a dollar to save a fraction of one. Purchases, sales, and gifts should make economic sense first; the tax planning is about timing and structuring what you'd do anyway. The best year-end moves, conversions, harvesting, bunching, cost nothing but attention.
Common questions
- What's the biggest December move?
- Depends on income. Low income = Roth conversion. High income = tax-loss harvesting + charitable bunching. Business owners = Section 179 or accelerated retirement contributions.
- When should year-end planning actually start?
- October or November, when there's enough of the year on the books to project accurately and enough calendar left to act. Brokerages and plan administrators get slow in late December; so does everyone's attention.
- Is there any way to undo a Roth conversion?
- No. Recharacterization of conversions was eliminated years ago. Size the conversion against a real income projection, because the number is final at midnight December 31.
- Do charitable gifts by credit card count if I pay the card in January?
- Yes. A gift charged by December 31 is deductible that year regardless of when the card is paid. Checks count when mailed. Stock gifts count when the transfer completes, which takes lead time.
Related
Tax Planning
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Personal Income Tax Preparation
Federal and state 1040 preparation with year-round planning. We handle W-2, 1099, K-1, rental, and crypto income for individuals in Florida and all 50 states.
Related tax topics
Required Minimum Distributions
RMDs from traditional IRAs and 401(k)s are due by December 31 starting at age 73. Missing one costs 25% of the missed amount, 10% with timely correction.
Filing a Tax Extension
Form 4868 extends the filing deadline from April 15 to October 15, not payment. Estimate and pay what you owe by April 15 or penalties and interest accrue.
Quarterly Estimated Tax Payments
Quarterly estimates are due April 15, June 15, September 15, and January 15. Safe harbor is 90% of current-year or 100% of prior-year tax. Who has to pay.
Corporate Tax Extension
S-corps and partnerships file Form 7004 by March 15 for a September 15 extension. C-corps follow April 15 to October 15. Deadlines by entity and the K-1 impact.