The last few months of the year are the most valuable window for tax planning, because most strategies must be executed before December 31 to count for that tax year. Waiting until you file in the spring closes off nearly every meaningful option except IRA contributions. A short, focused checklist in Q4 can meaningfully lower what you owe.

Review Your Capital Gains and Losses

Before the year ends, look at your taxable brokerage accounts to see your realized gains and losses so far, along with unrealized positions you might sell.

• Harvest losses on underperforming positions to offset realized gains elsewhere in your portfolio
• If losses exceed gains, remember up to $3,000 can offset ordinary income, with the rest carrying forward
• Watch for mutual fund capital gains distributions, typically paid in November or December, which can create a tax bill even if you didn’t sell anything
• Avoid the wash-sale rule if repurchasing a similar position, waiting at least 31 days before buying back the identical security

Reviewing gains and losses together lets you decide whether realizing additional gains this year (if you’re in an unusually low bracket) or harvesting more losses makes more sense.

Max Out Retirement Contributions

Employer retirement plans like 401(k)s have a calendar-year contribution deadline, meaning your last paycheck of December is typically your final chance to contribute for the year. IRAs are more flexible, allowing contributions up until the tax filing deadline the following spring.

Account	Contribution Deadline
401(k) / 403(b)	December 31 (via payroll)
Traditional or Roth IRA	Tax filing deadline (following April)
HSA	Tax filing deadline (following April)
SEP-IRA (self-employed)	Tax filing deadline, including extensions

Check your year-to-date 401(k) contributions in November so you have time to adjust your final paychecks if you’re behind pace to hit the annual limit or capture your full employer match.

Plan Charitable Giving Strategically

Charitable contributions must be made by December 31 to count for the current tax year, and how you give can matter as much as how much you give.

1. Donate appreciated securities instead of cash — You avoid capital gains tax on the appreciation while still deducting the full fair market value, if you itemize
2. Consider a Donor-Advised Fund — Contribute a larger lump sum in one year to clear the itemization threshold, then distribute grants to charities over several future years
3. Use Qualified Charitable Distributions (QCDs) if you’re 70½ or older — Donating directly from an IRA satisfies part or all of your RMD without adding to taxable income
4. Bunch multiple years of giving into one tax year if your itemized deductions typically fall just under the standard deduction

Keep receipts and acknowledgment letters for any donation, since deductions above certain thresholds require specific documentation.

Take Required Minimum Distributions

If you’re subject to required minimum distributions (RMDs) from a traditional IRA or 401(k), the deadline is typically December 31 (the first RMD year allows a delay until April 1 of the following year, though that creates two RMDs in one year). Missing an RMD deadline can trigger a substantial excise tax penalty on the amount not withdrawn.

Confirm your RMD amount with your custodian well before year-end, since it’s calculated using your account balance as of the prior December 31 and an IRS life expectancy factor. If you don’t need the cash, a Qualified Charitable Distribution can satisfy the RMD while keeping the amount out of your taxable income entirely.

Review Flexible Spending Account Balances

Unlike HSAs, most FSAs operate on a use-it-or-lose-it basis, though some plans offer a grace period or a small carryover amount. Check your remaining FSA balance and schedule any eligible medical, dental, or vision expenses before the plan’s deadline to avoid forfeiting unused funds.

Time Income and Deductions Where Possible

If you have some control over when income or deductible expenses land, such as through self-employment invoicing or estimated tax payments, consider whether shifting income or expenses between this year and next could reduce your total tax across both years. This is most useful when you can reasonably predict being in a different tax bracket in the following year.

Frequently Asked Questions

What is the single most time-sensitive year-end tax move?

401(k) contributions, since they’re tied to payroll and typically cannot be made after your last December paycheck. IRA and HSA contributions have more flexibility into the following spring.

Can I still make an IRA contribution after December 31?

Yes, IRA contributions for a given tax year can be made up until the tax filing deadline the following April, giving you extra time compared to workplace plans.

Does donating appreciated stock really save more than donating cash?

Often yes, if you’ve held the stock long-term and it has appreciated significantly, since you avoid capital gains tax on the appreciation while still claiming the deduction for the full value, subject to itemizing and AGI limits.

What happens if I miss my RMD deadline?

The IRS can impose an excise tax on the amount not withdrawn, though it has been reduced in recent years and may be further reduced if corrected promptly. It’s best to withdraw on time or set up automatic RMD distributions with your custodian.

Final Thoughts

Most of the highest-value tax moves have a hard December 31 deadline, which is why a focused year-end review beats scrambling in April. This article is general education, not personalized tax or legal advice, so consult a qualified tax professional to build a year-end checklist tailored to your accounts, income, and goals.