What Actually Closes on December 31



Every year, sometime around the second week of December, the same sentence starts appearing everywhere. You have until December 31.

It is repeated by brokerages, by newsletters, by the automated email your plan administrator sends. And it is close enough to true that almost nobody checks it.

But year-end tax deadlines are not one deadline. They are six or seven separate doors, and they close at different hours. Two of them are already shut by the time most people start paying attention. Two others stay open well into the following spring, which means the December scramble to get through them was never necessary.

Knowing which is which does not require a tax professional or a strategy. It requires a calendar with the correct dates on it.

The Door That Closes First

Start with the one that surprises people, because it is the only one that closes before the date everyone is watching.

If you sell an investment at a loss and intend to use that loss on your return, the loss can be disallowed by what the IRS calls a wash sale. The definition is specific: a wash sale occurs when you sell stock or securities at a loss and, within 30 days before or after the sale, you acquire substantially identical stock or securities.

Read the phrase before or after again, because it is doing more work than it looks like it is doing.

The window is not thirty days. It is sixty-one — thirty days on each side of the sale, plus the day itself. And it does not only catch deliberate repurchases. It catches an automatic dividend reinvestment. It catches a recurring monthly contribution that lands on the fifteenth. It catches a purchase made inside an IRA, including a Roth. It catches a purchase made by a spouse.

The practical consequence is a date, not a rule. If a sale happens on December 31, the window extends into the following January — and anything that lands in that window can reach backward and disallow the loss. If a purchase happened on December 20, the sale on December 31 is already inside the window.

So the door that people think closes at midnight on the thirty-first actually needs to be walked through with about a month of clearance on either side. In practice, the decisions that make a loss usable are made in late November and early December, not on New Year's Eve.

The phrase carrying the most weight in the rule is substantially identical, and the IRS does not define it with a bright line. Selling one company's shares and buying a different company's shares in the same industry is not the same transaction as selling shares and buying them back. Where exactly two index funds tracking similar markets fall is the kind of question that has a real answer for your specific holdings and no useful general one — which is precisely why it belongs with someone who can see the actual positions.

Nothing about this is a reason to sell anything. It is a reason to know that the sale date and the deadline date are not the same date.

The Doors That Do Close on the Thirty-First

Four things really do end when the year does.

Required minimum distributions. If you have reached the age at which withdrawals from a traditional IRA or a workplace plan become mandatory — currently 73 — the amount for the year has to be out of the account by December 31. There is one exception, and it is a first-timer's exception only: for your first RMD, the deadline is April 1 of the following year. That extension applies once. The second RMD is still due by December 31 of that same year, which means anyone who uses the extension takes two distributions in one calendar year and reports both as income in that year.

That is a detail worth reading more than once, because the extension is often described as a benefit and it is not self-evidently one. It moves a withdrawal, not a tax bill — and it stacks two withdrawals into a single year's income.

The IRS spells the sequence out with dates. Someone who reaches 73 in a given year has a first distribution due by April 1 of the following year, calculated on the balance from two Decembers earlier — and a second distribution due by December 31 of that same following year, calculated on the more recent balance. Two withdrawals, one tax year, both reported together.

Whether that is worth doing depends entirely on which year you would rather have the income land in, which is a question about your own bracket and not something a general rule can answer.

A Roth conversion. If money is moving from a traditional account to a Roth, the transaction has to be completed within the calendar year to belong to that year's taxes. There is no grace period, and — unlike a contribution — there is no undoing it later.

Charitable giving. A gift counts for the year in which it is made. December 31 is genuinely the line.

Realizing a gain or loss. The trade has to settle in the year you want it counted in. This is the one people are actually thinking of when they say December 31, and they are right about it. They are just wrong about how far in advance the decision has to be made, for the wash sale reason above.



The Doors That Stay Open

Here is where the December scramble becomes unnecessary.

An IRA contribution. Contributions for a given tax year can be made until the due date of that year's return — April 15 of the following year. The IRS says so plainly in its own year-end reminders: contributions for one year can be made until the filing deadline of the next. Someone who is short of the limit on December 31 has not missed anything. They have three and a half months.

This is the single most commonly misplaced deadline in the whole set, and the reason is structural rather than anything to do with taxpayers. December is when the reminder emails go out, because December is when attention is available. The date in the email and the date in the tax code are not the same date.

A 401(k) contribution. This one goes the other way — the real deadline is earlier than December 31, and for a reason that has nothing to do with the IRS.

Contributions to a workplace plan come out of payroll. They can only be made on a day you are paid. Which means the last usable date is your final paycheck of the year, and the practical cutoff is earlier still: most payroll systems need the change submitted a pay period or two ahead to process it. Someone who decides on December 28 to top up their plan for the year has, in most cases, already missed it — not because a deadline passed, but because there is no paycheck left to take it out of.

The calendar year sets the limit. Payroll sets the deadline.

The Numbers for 2026

The limits change annually, and the IRS announced 2026 in November of last year.

The employee contribution limit for 401(k), 403(b), governmental 457 plans, and the federal Thrift Savings Plan is $24,500, up from $23,500. For participants 50 and older, the catch-up is $8,000, bringing the total to $32,500. There is a separate, higher catch-up for employees aged 60 through 63 — $11,250 instead of $8,000 — created under SECURE 2.0.

The IRA limit is $7,500, up from $7,000. The catch-up for those 50 and over is $1,100, for a total of $8,600.

On the loss side, the arithmetic has not moved in a long time. Capital losses offset capital gains first. If losses exceed gains, the excess reduces ordinary income up to $3,000 per year — $1,500 if married filing separately. Anything beyond that is not lost; it carries forward to later years, indefinitely, until it is used.

That carryforward is the part most worth internalizing, because it removes the urgency the December emails create. A loss that cannot be used this year is not a loss that expires. It waits.

A Note From Somewhere Else

I write about American markets from Korea, and the difference in how the two countries handle this is the thing that made me notice the deadlines in the first place.

In Korea, the year-end settlement happens in January and February, and your employer does most of it. Documents are gathered, submitted through a government portal, and the adjustment shows up in a spring paycheck. The individual's job is largely to supply paperwork. The deadline that matters is a submission deadline, and it arrives after the year it applies to.

The American version puts the individual inside the year, making decisions while it is still running. Several of the levers stop working the moment the year ends. That is a genuinely different relationship to a calendar, and it is why the December reminder emails exist at all — they are compensating for a system that requires action before a boundary rather than paperwork after one.

Neither arrangement is better. But if you grew up with one and now live under the other, the reminder emails will read as more urgent than they are, and the ones that matter will not stand out from the ones that do not.



What This Is Not

It is not tax advice. I am not an accountant and not an advisor. Everything above is a description of when things happen, not a recommendation about what to do. The dates are the IRS's; the decisions are yours, and the ones with real money attached are worth taking to someone licensed.

It is not an argument for doing something in December. The most common outcome of reading a piece like this should be recognizing that a deadline you were worried about is in April. Urgency is what the reminder emails are selling. The calendar is what they are describing, and the calendar is calmer than the email.

It is not complete. Estimated tax payments, health savings accounts, employer plan true-ups, state-level rules, and several other doors all have their own dates. The six above are the ones that come up most often and get confused most reliably.

It is not stable forever. Contribution limits change every year, and SECURE 2.0 has staggered provisions still phasing in. The 2026 figures are current; the structure is what persists.

The Shape of It

Sorted by when they actually close, rather than by when they are advertised:

Early December, effectively — anything involving a loss you intend to use, because the wash sale window reaches thirty days in both directions.

Your last paycheck — workplace plan contributions, whenever that lands.

December 31 — required distributions, Roth conversions, charitable gifts, and the trade date of any gain or loss.

April 15 — IRA contributions for the year that just ended.

One list, four different closing times. The version that lives in most people's heads has all of them at midnight on the thirty-first, which produces exactly the wrong behavior in both directions: rushing the things that can wait, and missing the things that already closed.

The dates are public, unchanging within a year, and free to look up. Which makes this one of the few places in personal finance where the entire advantage comes from reading a calendar correctly.

Data as of August 31, 2026. Sources: IRS IR-2025-111 (2026 contribution limits), IRS Topic No. 409 (capital gains and losses), IRS Publication 550 (wash sales), IRS retirement plan and IRA RMD FAQs, IRS IRA year-end reminders.

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Visuals on this post are AI-generated. The author works with AI as a research and drafting assistant; topics, judgments, and final edits are the author's own. This post is observation, not investment advice. See full Disclaimer for details.

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