Year-End Tax Checklist: 6 Moves to Make Before December 31

The final days of 2025 are ticking away, and for millions of Americans, the December 31 deadline represents more than just New Year's Eve celebrations. It's the last chance to make several financial moves that could significantly impact your tax bill—both this year and for years to come.

With the One Big Beautiful Bill Act ushering in substantial tax law changes starting January 1, 2026, this year's deadline carries unusual urgency. Here are six moves financial advisors say you should consider before the ball drops.

1. Max Out Your 401(k) Contributions

While you have until April 15, 2026, to contribute to an IRA for the 2025 tax year, workplace retirement plans like 401(k)s and 403(b)s have a hard December 31 deadline.

For 2025, you can contribute up to $23,500 to these accounts—or $31,000 if you're 50 or older, thanks to the catch-up contribution provision. Every dollar you contribute reduces your taxable income dollar-for-dollar if you're using a traditional (pre-tax) account.

If you haven't maxed out your contributions, contact your HR department immediately. Some employers can process additional payroll deductions even at this late date, and the tax savings can be substantial—especially for high earners.

2. Fund Your Health Savings Account

Health Savings Accounts remain one of the most tax-advantaged vehicles available, offering what financial planners call the "triple tax advantage": contributions are tax-deductible, earnings grow tax-free, and withdrawals for qualified medical expenses are also tax-free.

For 2025, you can contribute up to $4,300 for self-only coverage or $8,550 for family coverage. Unlike 401(k)s, you can make HSA contributions until April 15, 2026, for the 2025 tax year—but why wait? Getting money invested earlier means more time for tax-free growth.

3. Harvest Your Investment Losses (and Gains)

Tax-loss harvesting—selling investments that have declined in value to offset capital gains—is a year-end staple. If your losses exceed your gains, you can deduct up to $3,000 against ordinary income, with excess losses carrying forward to future years.

But here's the twist for 2025: with tax rates expected to remain stable in 2026 under the new law, there's less urgency to defer gains than in years when rate increases loomed. Some advisors are actually recommending selective gain harvesting for clients in lower tax brackets who expect their income to rise.

Remember the wash-sale rule: if you sell a security at a loss, you can't buy it back (or something "substantially identical") within 30 days, or you lose the tax benefit.

4. Make Charitable Contributions Before the Rules Change

Charitable giving becomes less valuable for many taxpayers starting in 2026. Under the new law, itemizers will only be able to deduct charitable gifts that exceed 0.5% of their adjusted gross income. Additionally, the top tax bracket drops from 37% to 35%, reducing the value of charitable deductions for high earners.

If you've been considering a significant charitable contribution, making it in 2025 could provide meaningfully more tax benefit than waiting until next year.

For those with appreciated stock, donating shares directly to charity rather than selling them first eliminates capital gains tax entirely while still providing the full fair-market-value deduction.

5. Use Your Gift Tax Exclusion

The annual gift tax exclusion allows you to give up to $19,000 per recipient in 2025—$38,000 if you're married and gift-splitting with your spouse—without any gift tax consequences or reporting requirements.

This is a "use it or lose it" provision. Unused exclusion doesn't carry forward. If you've been planning to help family members with down payments, education expenses, or other financial goals, completing those gifts before December 31 maximizes your tax-efficient giving capacity.

6. Complete Energy Efficiency Improvements

Both major residential clean energy tax credits—the Residential Clean Energy Credit and the Energy Efficient Home Improvement Credit—were repealed for property placed in service after December 31, 2025.

This means if you've been considering solar panels, a heat pump, new windows, or other qualifying improvements, the project must be completed (not just paid for) by year-end to qualify for the credit.

For solar installations, the credit can be worth 30% of the total cost—potentially tens of thousands of dollars for larger systems. That benefit disappears entirely for projects completed in 2026.

The Bottom Line

Year-end tax planning always matters, but this year it matters more than usual. The combination of expiring credits, changing deduction rules, and new provisions taking effect in 2026 creates a narrow window for optimization.

Not every strategy applies to every taxpayer, and individual circumstances vary enormously. But with just days remaining, even small actions—an extra 401(k) contribution, a charitable donation of appreciated stock, or finally pulling the trigger on that solar installation—could translate into meaningful tax savings.

The clock is ticking. Make it count.