On the standard January-through-December calendar, the 4th quarter runs from October 1 through December 31, covering the final 92 days of the year.1Internal Revenue Service. Tax Calendar October and December each have 31 days, November has 30. The IRS treats these three months as Q4 for individual income tax purposes, and most businesses that have not chosen a different fiscal year close their books on the same schedule.
If you follow a different fiscal year, your Q4 falls somewhere else on the calendar. The quarter is always the final three months of your twelve-month accounting period, wherever those months land.
When Q4 Falls on a Non-Calendar Fiscal Year
Federal Government
The United States federal government’s fiscal year begins October 1 and ends September 30.2U.S. Senate Budget Committee. Basic Federal Budgeting Terminology That makes the federal Q4 July 1 through September 30. Agencies rush to obligate remaining funds before the September 30 close, which is why federal contract activity spikes in summer.
Retailers
Many large retailers end their fiscal year on January 31 rather than December 31. Their Q4 runs roughly November through January, capturing holiday sales along with the returns and gift-card redemptions that follow.
Nonprofits and Universities
Many nonprofits and schools operate on a July 1 through June 30 fiscal year, which lines up with the academic calendar. Under that schedule, Q4 is April 1 through June 30, so the year-end financial push happens in spring.
Retirement Deadlines Tied to Calendar Q4
For anyone on the standard calendar, Q4 is the last chance to lock in several tax-year moves. Not every account uses the same cutoff.
401(k), 403(b), and 457 Plans
Employer-plan contributions must go through payroll by December 31 to count for the current tax year. For 2026, the elective deferral limit is $24,500. Workers 50 and older can add a catch-up of up to $8,000, for a total of $32,500. A higher catch-up of $11,250 applies at ages 60, 61, 62, and 63, bringing that combined maximum to $35,750.3Internal Revenue Service. 401(k) Limit Increases to $24,500 for 2026, IRA Limit Increases to $7,500 Because the money moves through payroll, adjust your election early enough that the change hits your final paychecks of the year.
IRAs and HSAs
IRA and HSA contributions do not stop at December 31. You have until the federal tax filing deadline of the following year, typically April 15. For 2026, the IRA limit is $7,500, plus a $1,100 catch-up at 50 or older. The HSA limit is $4,400 for self-only coverage and $8,750 for family coverage, plus a $1,000 catch-up at 55 or older.3Internal Revenue Service. 401(k) Limit Increases to $24,500 for 2026, IRA Limit Increases to $7,500 Contributions made between January 1 and April 15 can be applied to the prior tax year.
Required Minimum Distributions
If you are 73 or older, your annual RMD from traditional IRAs and most employer retirement plans must come out by December 31. Your very first RMD can be delayed until April 1 of the year after you turn 73, though that pushes two distributions into the same tax year. Missing an RMD triggers a 25 percent excise tax on the amount you should have withdrawn, which drops to 10 percent if you correct the shortfall within two years.4Internal Revenue Service. Retirement Topics – Required Minimum Distributions (RMDs)
Fourth-Quarter Estimated Tax Payment
If you pay quarterly estimated taxes, the Q4 installment is due January 15 of the following year.5Office of the Law Revision Counsel. 26 USC 6654 – Failure by Individual to Pay Estimated Income Tax For the 2026 tax year, the payment is due January 15, 2027.
To avoid an underpayment penalty, your total estimated payments and withholding must equal at least the lesser of 90 percent of your current-year tax or 100 percent of your prior-year tax. If your prior-year adjusted gross income was over $150,000 ($75,000 if married filing separately), the prior-year safe harbor rises to 110 percent.5Office of the Law Revision Counsel. 26 USC 6654 – Failure by Individual to Pay Estimated Income Tax The current IRS underpayment rate is 7 percent per year, compounded daily on the shortfall.6Internal Revenue Service. Interest Rates Remain the Same for the First Quarter of 2026
One useful alternative: file your full return by January 31 and pay the entire balance, and the IRS automatically waives the Q4 underpayment penalty.5Office of the Law Revision Counsel. 26 USC 6654 – Failure by Individual to Pay Estimated Income Tax
Other Year-End Deadlines
Charitable Contributions
To claim a charitable deduction for the current tax year, your gift has to be made by December 31. Any donation of $250 or more requires a written acknowledgment from the organization showing the amount and date. Starting with the 2026 tax year, taxpayers who take the standard deduction can also deduct up to $1,000 in cash charitable contributions, or $2,000 if married filing jointly.7Internal Revenue Service. Topic No. 506, Charitable Contributions That benefit used to be available only to itemizers.
Flexible Spending Accounts
Most health-care FSAs run on a calendar year, so unspent funds are at risk after December 31. Your employer’s plan may offer a grace period of up to two and a half months (through March 15) or a carryover of a limited amount, but not both.8Internal Revenue Service. Eligible Employees Can Use Tax-Free Dollars for Medical Expenses Check your plan documents in Q4 before scheduling any late-year medical spending.
Withholding Adjustments
Q4 is a good time to revisit your paycheck withholding, particularly if last year’s return produced a big balance due or a big refund. When you submit a new Form W-4, your employer has up to 30 days to put the change into effect.9Internal Revenue Service. Publication 15 (2026), (Circular E), Employer’s Tax Guide Submitting it early in the quarter gives the adjustment time to show up in your remaining paychecks.
One quirk worth watching: Social Security tax (6.2 percent for employees) applies only to the first $184,500 of earnings in 2026.10Social Security Administration. Contribution and Benefit Base If your pay crosses that threshold during the year, the deductions stop and your net pay rises, then drops back in January when the cycle resets.
What Happens After Calendar Q4 Closes
Public companies with a December 31 fiscal year-end move straight into annual reporting once Q4 ends. The SEC requires each one to file a Form 10-K with audited financial statements, a discussion of business risks, and disclosure of material legal proceedings. The filing window depends on company size:
- Large accelerated filers: 60 days after fiscal year-end
- Accelerated filers: 75 days after fiscal year-end
- All other filers: 90 days after fiscal year-end
For a December 31 year-end, those deadlines fall in late February, mid-March, and late March.11U.S. Securities and Exchange Commission. Form 10-K For consumer-facing companies, Q4 revenue often makes up a disproportionate share of the year, which is why the Q4 earnings report tends to be the most closely watched disclosure of the cycle.