Year-End Tax Checklist 2026: 401(k), IRA, HSA Deadlines to Hit

The last few months of the year are your final window to lock in tax-advantaged moves before the calendar flips. Some deadlines are firm at December 31; others actually extend into next April. Use this checklist to make sure you're not leaving money — or tax savings — on the table.

The 6-Point Year-End Checklist

Max out your 401(k) by December 31. Unlike IRA and HSA contributions, 401(k) contributions must go through payroll and are locked to the calendar year — you cannot contribute after December 31 for the current tax year. Check your last few pay stubs to see if you're on pace for $24,500 ($32,500 or $35,750 with catch-up).
Fund your HSA — you have until the tax filing deadline. Unlike the 401(k), HSA contributions for 2026 can be made up until April 15, 2027 (the filing deadline) and still count for the 2026 tax year. That gives you extra time to top off the $4,400 self-only / $8,750 family limit.
Fund your IRA — same extended deadline. Traditional and Roth IRA contributions also have until the April filing deadline to count for the prior tax year, so you don't have to rush before December 31 if cash is tight right now.
Check your FSA balance before it disappears. Flexible Spending Accounts are generally "use it or lose it" — unused funds at year-end may be forfeited, unless your employer offers a grace period or small carryover. Schedule any remaining eligible medical expenses before your plan year ends.
Review your W-4 withholding. Big life changes this year — a new job, marriage, a child, a raise — can throw off your withholding. Adjust now so you're not surprised with a big bill (or a penalty) at filing time.
Gather your tax documents as they arrive. Start a folder for W-2s, 1099s (NEC/MISC/INT/DIV/B), 1098 (mortgage interest), 1098-E (student loan interest), 1095-A/B/C (health coverage), and K-1s so you're not scrambling in April.

Don't Forget: Charitable Giving Has a Hard December 31 Deadline

Unlike HSA and IRA contributions, donations to qualified charities must be made by December 31 to count toward that tax year's deduction — there's no extension into the following spring. If you plan to itemize and want the deduction this year, make sure the donation, and its receipt, are dated by year-end.

Quick Reference: Which Deadlines Extend Into Next Year?

Item	Deadline
401(k) contributions	Hard deadline: December 31
IRA contributions (Traditional/Roth)	Extended: until the April filing deadline
HSA contributions	Extended: until the April filing deadline
Charitable donations	Hard deadline: December 31
FSA spending	Hard deadline: end of plan year (typically December 31, unless your plan allows a grace period)

Frequently Asked Questions

If I max my HSA in March 2027, does it count for 2026 or 2027? You choose — when you contribute, you (or your HSA provider) designate which tax year the contribution applies to, as long as it's within the allowed window and under that year's limit.

What if I can't afford to max everything out by December 31? Prioritize: capture your full 401(k) match first, since that's locked to payroll timing, then work on your IRA and HSA — you can still fund those into next spring while you catch up.