Once the ball drops, roughly 80% of tax planning becomes impossible — 2026's numbers are locked. Here are the twelve moves worth making in the next 96 days, including three that are brand new this year.
For everyone
- Max the tax-advantaged accounts. 401(k) deferrals must be in by December 31. IRAs and HSAs give you until April 15, but December money compounds three months longer.
- Harvest investment losses against gains — and remember the wash-sale rule: don't rebuy the same security within 30 days. (Worth noting: wash-sale rules still don't apply to crypto.)
- New for 2026 — the non-itemizer charitable deduction. Up to $1,000 ($2,000 joint) of cash gifts to public charities now deducts even if you take the standard deduction. Cash to a qualifying charity by December 31 — donor-advised funds don't count for this one.
- New for 2026 — itemizers face a 0.5% AGI floor. Only giving above 0.5% of your AGI is deductible now. Translation: many small-giving years produce nothing; bunching two or three years of gifts into one big year matters more than ever.
- Check the SALT window. The cap is $40,400 this year but phases back toward $10,000 once MAGI passes $505,000. If you're near the line, income timing (deferring a bonus, realizing losses) can protect tens of thousands of deduction.
- Consider a Roth conversion if 2026 income dipped — conversions must complete by December 31, not April.
For business owners
- Buy and place equipment in service by December 31. 100% bonus depreciation is permanent now — but the deduction lands in the year the asset is placed in service, not ordered. A delivery date of January 2 costs you a year.
- Fund retirement like an owner. Solo 401(k)s should be established by year-end; a cash-balance plan can shelter six figures for high-profit years — but not if you start in March.
- Review your S corp salary before the final payroll run — the reasonable-compensation check is a December fix, not an April one.
- Settle bonuses and family payroll — kids legitimately on payroll, year-end bonuses, and accountable-plan reimbursements all need to run through actual December payroll.
- Prepay smartly if cash-basis — January rent, insurance, and software renewals paid in December deduct in 2026.
- Do the entity math for 2027. If the LLC-to-S-corp switch makes sense, a clean January 1 effective date beats a mid-year mess. The analysis takes one meeting.
The pattern behind every December regret: the move was known in October and attempted on December 28. Pick your three biggest levers now.
Want a personal version of this list with your actual numbers? Book a year-end planning call — this is exactly what they're for.
