Busy season accounting: a playbook for tax firms

Busy season accounting works best as four phases with different jobs. October to December is for engagement letters, organizers, capacity math and software decisions. January and February are for intake and triage. March 15 is the pass-through wall. April is extension triage, and the fall closes out on September 15 and October 15. Plan each phase separately and you'll find review, not prep, is the queue that sets the pace.

What does busy season accounting look like month by month?

For a calendar-year client base, busy season is shaped by three federal filing dates covering six return types, and each has an extension date that creates a second, smaller season later in the year. The dates below come from IRS Publication 509, Tax Calendars and the Instructions for Form 7004. When a date lands on a weekend or legal holiday, it moves to the next business day.

• March 15: Form 1065 and Form 1120-S, plus the K-1s that go to partners and shareholders. Extended with Form 7004 to September 15.
• April 15: Form 1040, Form 1120 and Form 1041. The 1040 extends with Form 4868 to October 15, the 1120 with Form 7004 to October 15, and the 1041 gets a 5½-month extension to September 30.
• May 15: Form 990 for calendar-year exempt organizations (May 17 in 2027, because the 15th is a Saturday). Extended with Form 8868 to November 15.

Every date on that list is a filing date, not a payment date. An extension buys time to file. It does not move the tax owed, which is why April is as much about estimates as it is about returns.

What should a firm do before busy season starts?

Most of what decides how a busy season goes is settled between October 15 and December 31. The first two weeks of October belong to the extension deadline, so planning starts after that.

1. Send engagement letters with dates in them. Put a document deadline in the letter itself, and say what happens after it: the return goes on extension.
2. Send organizers in December. Clients who have it before the holidays start collecting as W-2s and 1099s arrive.
3. Do the capacity math in reviewer hours. Count returns by type and complexity, then count the hours your reviewers actually have between February 1 and April 15. Preparer capacity is easier to flex with seasonal staff. Reviewer capacity is not, because the people who can sign off are the ones you have.
4. Clean up the client list. Late-document clients from last year, fee disputes and one-off engagements that took three times their budget are all decisions to make now, not in March.
5. Make every tooling decision before December. New software, new portals, new review tools and new workflows get chosen, set up and trained on in the fall. Nobody should be learning a system in February.

Preparers are right to resist mid-season tool changes, and a tool that goes in after January usually gets dropped by March. If you're weighing automation this year, the window is now. Our guide to scaling tax workflows with your current team covers the planning side of that decision in more depth.

How should firms run intake and triage in January and February?

Only start a return when its documents are complete. That single rule does more for January and February than anything else, because a half-prepared return sits in the queue, gets touched three times and still has to be picked up from scratch when the last 1099 arrives.

• Use a "ready to prep" status that means every expected document is in, checked against last year's return. The prior-year return is the best checklist you have: every payer, brokerage account and K-1 on it should show up again or have a reason it didn't.
• Sort the queue by deadline first and complexity second. Pass-through entities go to the front in January, because their K-1s hold up individual returns downstream.
• Expect corrected 1099s from brokerages in February and March. Consolidated brokerage statements are one of the most common reasons a finished return reopens, so flag clients with large brokerage activity and hold them until the corrections window has mostly passed.
• Track kickbacks by reason from day one. If the same errors keep coming back from review, fix them with a checklist in February, before volume peaks.

Why is review the bottleneck in busy season?

Review is the queue because it is the only step that can't be handed to more people. A firm can add seasonal preparers. It can't add partners and senior managers who are qualified to sign.

A simple example shows the problem. Say four reviewers each have 40 review hours a week, and an average return takes an hour to review, including one round of kickback. That is 160 returns a week, no matter how fast prep goes. If prep delivers 200, the extra 40 wait. By mid-March, the review stack sets the firm's pace.

Three habits keep the review queue under control:

1. Limit work in progress per reviewer. A reviewer with 60 returns assigned gets less done than one with 15 and a clear order. Assign in small batches.
2. Separate checking from judgment. Tying figures back to source documents is checking. Deciding whether a position holds up, whether an election makes sense, or what to tell a client is judgment. Reviewers should spend their hours on the second.
3. Shorten the kickback loop. Every return that goes back to prep and returns for a second review costs a reviewer the setup time twice. Catching clerical errors before a return reaches the reviewer removes most of those loops.

This is where automation earns its place in busy season. An automated first-pass review compares every figure on the draft return against the client's source documents and hands the reviewer a list of what doesn't match, with the document attached. Our guide to tax return review software covers what to look for.

How do you get pass-through returns out by March 15?

For most firms, March 15 is the hardest date of the year. Partnership and S-corp K-1s feed individual returns, so every 1065 or 1120-S that slips past March 15 pushes one or more 1040s into April or onto extension.

• Set an internal deadline of March 1 for pass-through documents. Anything not in by then goes on the extension list.
• File Form 7004 for extensions early rather than on March 14. Extensions filed in bulk at the last minute are how firms miss one.
• Tell partners and shareholders when their K-1 will arrive. An extended partnership means an extended 1040 for many owners, and clients should hear that from you in February, not in April.

Partnership work is also where manual data entry is heaviest. We looked at what automation can and can't do in can AI automate partnership tax returns.

How should firms handle the April crunch?

Decide the extension list by about March 25. After that date, a firm's best move is to finish what is ready and extend what is not, with a clean estimate of tax due.

1. Set a firm document cut-off (many firms use April 1) and hold to it. A return that comes in complete on April 10 is still a candidate for extension if the review queue is full.
2. Calculate payment estimates for every extended return. Form 4868 extends the time to file, not the time to pay, so an extended client with a balance due still needs a payment by April 15.
3. Don't forget the April 15 business and fiduciary returns. The 1120 and 1041 share the date with the 1040 and are easy to crowd out.

What happens during extension season?

Extension season is a second, compressed busy season with four deadlines of its own, and it usually gets less planning than it needs. September 15 covers extended 1065 and 1120-S returns, September 30 covers extended 1041s, October 15 covers extended 1040 and 1120 returns, and November 15 covers extended 990s.

The extended returns are the hardest ones: late documents, complex entities, clients who needed chasing. Plan the fall the way you planned January. Set document deadlines for extended clients in June, assign reviewers by August, and don't schedule the whole team's vacation for early September. Once October 15 passes, the cycle starts again with engagement letters and organizers.

Where does automation help most during busy season?

Automation helps most where work is repetitive and verifiable: reading documents, entering data and checking the return against its sources. It helps least when it arrives mid-season.

Filed does AI review and prep for mid-sized and high-volume firms. Filed Reviewer compares the draft return against the source documents line by line and gives the reviewer a cited list of issues, so checking happens before a return reaches a reviewer's desk. Filed Prep reads the client's documents and prepares the return. Prowork sits next to the tax software and reviews inline while the preparer works, and firms can teach it a correction once so it applies that fix every time after. Filed works with CCH Axcess, UltraTax, Lacerte, Drake and ProConnect, across 1040, 1065 with K-1, 1120, 1120-S, 1041 and 990 returns.

Firms using Filed Reviewer have seen 64% shorter review cycles and 42 minutes saved per return. The CPA still makes every judgment call and signs every return. Filed does the checking so the reviewer's hours go to the work only a reviewer can do.

Frequently asked questions

When is busy season for accounting firms?

For tax firms, busy season runs from January through April 15, with the heaviest weeks just before March 15 (partnership and S-corp returns) and April 15 (individual, C-corp and fiduciary returns). A second, smaller season runs from late summer through the September 15 and October 15 extension deadlines.

Should a firm change tax software or add new tools during busy season?

No. Choose, set up and train on new tools between October and December. Anything introduced after January competes with deadlines for the team's attention and usually doesn't get used properly until the following year.

When should a firm decide which returns to extend?

Build the pass-through extension list around March 1 and the individual extension list around March 25. Deciding early leaves time for payment estimates and client calls.

How quickly can Filed be running before busy season?

Filed Reviewer needs no integration with your tax software, so a firm can run its first reviews within a day. Filed works with CCH Axcess, UltraTax, Lacerte, Drake and ProConnect, and is SOC 2 compliant with ISO 27001 certification in progress. The fall is the right time to test it on last season's returns.

If you want to see how Filed fits into your firm's busy season plan, book a demo.

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