On the standard calendar, Quarter 1 runs from January 1 through March 31 — a 90-day window in non-leap years. That is the Q1 most individuals and businesses mean. Two other definitions matter if you deal with federal money or federal taxes: the federal government’s fiscal Q1 runs October 1 through December 31, and the IRS treats January through March as the first quarter of the tax year but doesn’t require the first estimated tax payment on that income until April 15.
Calendar Q1: January 1 Through March 31
This is the default. Personal budgeting, investment tracking, and most corporate financial reporting use it. Publicly traded companies file their quarterly earnings reports with the Securities and Exchange Commission within 40 to 45 days after the quarter ends, so calendar-Q1 numbers typically land in early May. Financial institutions issue account statements and interest summaries on the same three-month cycle.
Federal Fiscal Q1: October 1 Through December 31
The federal government runs on a different clock. By statute, the government’s fiscal year begins October 1 and ends September 30 of the following year.1Office of the Law Revision Counsel. 31 USC 1102 – Fiscal Year Federal fiscal Q1 is therefore October through December — what most people think of as the last three months of the calendar year.
This matters if you work with federal contracts or grants. Appropriations, procurement, and grant activity reset each October 1, and Q1 spending reports cover October through December. The four federal fiscal quarters are:
- FY Q1: October 1 – December 31
- FY Q2: January 1 – March 31
- FY Q3: April 1 – June 30
- FY Q4: July 1 – September 30
IRS Q1 Estimated Tax Deadline
The IRS treats January through March as the first quarter of the tax year, but the payment due date on that income falls in the second calendar quarter: April 15.2Office of the Law Revision Counsel. 26 USC 6654 – Failure by Individual To Pay Estimated Income Tax For the 2026 tax year, that deadline is Wednesday, April 15, 2026, with no holiday shift.3Internal Revenue Service. When to File
Estimated payments apply to income without withholding — self-employment earnings, significant investment income, and similar sources. You only face an underpayment penalty if the tax on your return, after subtracting withholding credits, comes to $1,000 or more.2Office of the Law Revision Counsel. 26 USC 6654 – Failure by Individual To Pay Estimated Income Tax Under $1,000 owed, no penalty for skipping estimated payments.
All four estimated tax due dates for a calendar-year taxpayer in 2026:4Internal Revenue Service. Publication 509 (2026), Tax Calendars
- 1st installment (Q1 income): April 15, 2026
- 2nd installment (Q2 income): June 15, 2026
- 3rd installment (Q3 income): September 15, 2026
- 4th installment (Q4 income): January 15, 2027
Safe Harbor
You can avoid the underpayment penalty even if you owe money at filing time. Estimated payments for 2026 must cover at least the smaller of 90 percent of your 2026 tax liability or 100 percent of the tax you owed for 2025. If your 2025 adjusted gross income was above $150,000 ($75,000 if married filing separately), the prior-year figure rises to 110 percent of your 2025 tax.5Internal Revenue Service. 2026 Form 1040-ES Estimated Tax for Individuals
How to Pay
Form 1040-ES includes paper vouchers you can mail. The IRS also accepts payment through Direct Pay (free bank transfers at IRS.gov/Payments), EFTPS (free but requires enrollment), your IRS Online Account, debit card, credit card, or digital wallet through a third-party processor for a fee, and the IRS2Go mobile app.5Internal Revenue Service. 2026 Form 1040-ES Estimated Tax for Individuals
Employer Q1 Filings
If you run a business with employees, the end of Q1 triggers filings on top of your own estimated taxes.
Form 941
Form 941 reports income tax withheld from wages, Social Security tax, and Medicare tax for the quarter. The Q1 return is due April 30, 2026. If you deposited all taxes for the quarter on time and in full, the deadline stretches to May 10, 2026.6Internal Revenue Service. Instructions for Form 941
FUTA Deposits
Federal unemployment tax runs on a quarterly deposit schedule. If your cumulative FUTA liability exceeds $500 by the end of Q1, deposit it by April 30. If liability is $500 or less, carry it forward to the next quarter until the cumulative amount crosses the threshold.7Internal Revenue Service. Topic No. 759, Form 940 – Filing and Deposit Requirements
Corporate Q1 Estimated Tax
C-corporations pay estimated tax in four installments on the 15th day of the 4th, 6th, 9th, and 12th months of their tax year. For a calendar-year corporation, the first installment is due April 15, and the fourth falls December 15 rather than the following January. No penalty applies if the total tax for the year is under $500.8Office of the Law Revision Counsel. 26 USC 6655 – Failure by Corporation To Pay Estimated Income Tax
What Missing a Q1 Deadline Costs
Penalties compound the longer you wait, and the specific charge depends on what you missed.
For underpaid estimated tax, the IRS charges interest on the shortfall at the underpayment rate set each quarter under Section 6621.2Office of the Law Revision Counsel. 26 USC 6654 – Failure by Individual To Pay Estimated Income Tax For the first quarter of 2026 (January through March), the underpayment rate for individuals is 7 percent. It drops to 6 percent starting April 1, 2026.9Internal Revenue Service. Bulletin No. 2026-8 Interest runs from the missed due date until you pay.
For a required return that goes unfiled with tax owed — including quarterly employer returns like Form 941 — the failure-to-file penalty is 5 percent of the unpaid tax per month or partial month the return is late, capped at 25 percent. When failure-to-file and failure-to-pay penalties both apply in the same month, the failure-to-file penalty is reduced by the failure-to-pay amount.10Internal Revenue Service. Failure to File Penalty
When Q1 Doesn’t Start January 1
Some organizations define Q1 to match their operating cycle rather than the calendar.
Many retailers start their fiscal year in late January or early February so holiday returns land in the prior year’s final quarter instead of bleeding into Q1 results. Some do this by electing a 52-53 week tax year, which always ends on the same day of the week, such as the last Saturday in January. The year alternates between 52 and 53 weeks to stay roughly aligned with the calendar.11eCFR. 26 CFR 1.441-2 Election of Taxable Year Consisting of 52-53 Weeks A retailer’s Q1 might then run from early February through late April.
Colleges and universities commonly begin their fiscal year in July, August, or September to align with the fall semester. Under that structure, Q1 covers the period when tuition arrives and enrollment finalizes, matching billing cycles and staffing decisions.