The IRS opened US tax season 2026 on January 26 and set April 15 as the deadline for tax year 2025 returns. About 164 million individual returns were expected before that date. For a firm partner, though, the number that decides the season is not on the IRS calendar. It is how many of those returns your team can prepare and you can review without the season running you.
US tax season 2026 is the stretch in which the IRS accepts and processes federal returns for tax year 2025. It ran from January 26 through the April 15 filing deadline, with a six-month extension available to October 15. Two things set it apart from the season before.
First, the calendar was unforgiving as always: partnership and S corporation returns came due in March, and quarterly estimated payments landed across April, June, and September. Second, the One Big Beautiful Bill added new deductions for tips, overtime, and seniors, claimed on a new Schedule 1-A, which put fresh review steps on ordinary individual returns.
Here is what it really comes down to. The 2026 season did not get harder because of its dates. It got harder because more judgment now sits behind each return, and judgment is the one thing a short-handed firm cannot buy in April. The good news is that the constraint is fixable, and the window to fix it is the quiet stretch you are in right now, before the next deadline. We will come back to that window at the end.
When does the 2026 tax season start, and what are the key deadlines?
The 2026 tax season started on January 26, when the IRS began accepting tax year 2025 individual returns. The deadlines that follow are the ones that actually shape a firm's workload.
| Date | Milestone |
|---|---|
| January 26, 2026 | IRS begins accepting 2025 individual returns |
| March 16, 2026 | Calendar-year partnership and S corporation returns |
| April 15, 2026 | Individual returns and first-quarter estimated payments |
| June 15, 2026 | Second-quarter estimated payments |
| September 15, 2026 | Third-quarter estimated payments |
| October 15, 2026 | Extended individual returns |
| January 15, 2027 | Fourth-quarter estimated payments for 2026 |
The IRS confirmed the start date and the April deadline when it opened the 2026 filing season, and expected about 164 million individual returns for tax year 2025. Per the IRS Taxpayer Advocate Service's list of important 2026 tax dates, calendar-year partnerships and S corporations filed by March 16, individuals by April 15, and extended individual returns by October 15, with estimated payments due April 15, June 15, September 15, and January 15, 2027.
For a partner, these dates cluster in a way no amount of planning smooths out. March pulls in the pass-through returns while individual work is already stacking up, and the April wall arrives with estimated payments riding alongside it. The calendar has not changed. What sits inside it has.
What is new for the 2026 filing season?
The biggest change for the 2026 filing season came from the One Big Beautiful Bill, which created new deductions for tax year 2025 and a new form to claim them. The IRS published Schedule 1-A so taxpayers could report deductions for tips, overtime, car loan interest, and an enhanced deduction for seniors.
Under the IRS's Schedule 1-A guidance, workers can deduct up to $25,000 in qualified tips and up to $12,500 in qualified overtime, or $25,000 for joint filers, and older taxpayers can claim an enhanced deduction of $6,000 per person, or $12,000 for a qualifying couple. Each of these deductions phases out at higher incomes, so eligibility turns on the client's modified adjusted gross income (MAGI).
Each new deduction is an eligibility test your preparers have to apply and your reviewers have to confirm. A return that used to be routine now carries a question about whether the tips are qualified, whether the overtime meets the definition, and whether the senior deduction survives the client's income. None of that is hard on its own. All of it is time, multiplied by every affected return, arriving in the same few weeks.
Why does the 2026 season land harder on short-staffed firms?
The 2026 season lands hardest on firms that were already short a reviewer. Preparation capacity is something you can add: you can hire a preparer, train one, or contract one. Review capacity is a different asset, because review is judgment, and your signature attests to that judgment.
Watch what the new deductions do to that chokepoint. Every return that touches tips, overtime, or the senior deduction now needs a second look for eligibility, and that second look belongs to your most experienced people, the same people who were already the bottleneck in April. Volume did not rise. The judgment behind each return did.
Partners tend to feel this in a fixed order. Deadlines start slipping. Quality gets uneven under load. Then someone good leaves, worn down by a season that asked too much. There is a quiet fourth cost that never shows up on a report: the work you turned away because you had no one left to review it.
How can your firm add reviewable capacity before the next deadline?
The window to fix a capacity problem is never April. It is the quiet stretch after April 15, before the fall deadlines, which is roughly where you are now. Building reviewable capacity takes a running start, and the firms that move through a season without drama built it in the months before the rush.
This is the problem we built Accountably to solve. We place trained offshore tax preparers and accountants inside your firm, ramped on your software and SOPs in about three to four weeks, so work reaches your desk having already passed a preparer, a senior, a quality check, and a final review. Four sets of eyes before it reaches yours. The signature, the opinion, and the final judgment stay with your firm. You sign; we make it signable.
That review chain is the point, not the seat count. Since 2022 we have worked with more than 20 US firms and made more than 30 placements. One tax-focused firm ran 310 returns in 10 weeks with our team and freed roughly 200 hours of its own people's time.
You should not take our word for any of this, and you do not have to. Before a single client file is on the line, we run a Free 40-Hour Proof Pilot: a fixed 40-hour block of your own representative work, prepared on your SOPs and put through the full review chain, so your reviewer grades real output before you commit. If a placement is not the right fit in the first 30 days, we replace them free, our 30-Day Fit Guarantee.
Don't trust us. Test us. If your firm is carrying this volume, start with a Proof Pilot.
Frequently asked questions
When did the 2026 tax season start?
The 2026 tax season started on January 26, when the IRS began accepting and processing tax year 2025 individual returns. The filing deadline was April 15, and a six-month extension moved that to October 15 for taxpayers who requested one.
When were 2025 business returns due in 2026?
Calendar-year partnerships and S corporations filed their 2025 returns by March 16. Individual returns were due April 15. Firms that needed more time filed extensions rather than miss the date.
What is Schedule 1-A?
Schedule 1-A is a new IRS form for tax year 2025. Taxpayers use it to claim the One Big Beautiful Bill deductions for tips, overtime, car loan interest, and the enhanced deduction for seniors, and it attaches to the Form 1040. Each deduction carries its own eligibility rules and income phase-outs.
How do the new 2026 deductions affect a firm's workload?
The new deductions add eligibility checks to ordinary individual returns, and those checks fall on a firm's reviewers. A return with tips or overtime now needs a second look it did not need last season. Across a full client base, that is real review time concentrated in the same filing weeks.