How to stop chasing clients for documents on extension

It’s July 8th. Eighteen returns went on extension back in April, and by now maybe six clients have sent anything since. The K-1 for the S-corp return is stuck behind a bookkeeper who has not closed May. October 15 is ninety-nine days out and does not feel real yet.

Chasing clients for documents on extension is a different problem than April’s version of the same job. Fewer returns are open, but the ones still open are usually the hard ones: multi-entity K-1s, basis calculations, a foreign account form that needs a partner’s sign-off. The fix is the same discipline that worked before April 15, restarted on a July calendar instead of a September one. Track one outstanding item per return, send the next request the day the September 15 entity deadline passes, and by late September the firm already knows which returns will make October 15 and which will not.

Why extension season creeps up on firms that feel caught up

April ends and the returns still open feel like a manageable list. Eighteen files, maybe twenty. That list does not shrink itself over the summer. It waits, and the same document-chasing math that ate 30% or more of tax season capacity, according to the AICPA Practice Management Survey, applies just as much to the twenty returns left on extension as it did to the two hundred that filed on time.

What makes extension season different is the shape of the delay. April’s missing documents are usually simple: a client has not gotten around to uploading a W-2 they already have. Extension-season delays are structural. A client’s K-1 does not exist yet because the partnership return that produces it has not been filed. A basis worksheet needs a bookkeeper the client does not control. A foreign account disclosure needs a signature from a partner who is traveling. None of these resolve with a single reminder email.

The September 15 entity deadline sets up the October 15 crunch

Partnerships and S-corps that filed Form 7004 on time get an automatic six-month extension to September 15. Individual returns, most trusts, and C-corps extended on Form 4868 or Form 7004 run to October 15. For any individual client who owns a stake in a partnership or S-corp, those two dates are not independent. The K-1 usually cannot exist until the entity return is filed, and the individual return usually cannot be finished until the K-1 arrives.

That leaves a real but narrow window, typically around four weeks, between September 15 and October 15 to collect the K-1, check it against the client’s other documents, and file. A firm that starts asking for the K-1 on September 16 is already behind. A firm that has been tracking which entities are still filing, and which clients are waiting on which K-1, can request the document the moment the entity return is done rather than the moment someone remembers to ask.

The IRS treats October 15 as a real filing deadline, not a soft target, and the penalty exposure for a late-filed extension return is the same as for any other late return. Treating the September-to-October window as a formality is the mistake that produces the October scramble.

Build a tax extension document checklist that survives to October

A list of open returns is not the same as a working checklist for October 15 extension deadline documents. The difference is a named blocker on every return, not a general “waiting on client” status, and a schedule that starts in July instead of the week before the deadline.

1. 1

   List every open return and its single blocker

   Not a general status of "waiting on documents." Name the exact item: the 2025 K-1 from Riverside Partners, the corrected 1099-DIV from the brokerage, the signed basis worksheet from the bookkeeper. A return with a named blocker is trackable. A return marked "incomplete" is not.

2. 2

   Separate entity-dependent returns from the rest

   Flag every individual return waiting on a K-1 from a partnership or S-corp the firm also prepares, or that the client has told you is extended elsewhere. These returns cannot move until September 15, so they need a different reminder schedule than a return that is simply waiting on a 1099.

3. 3

   Restart requests the first week of July

   Send a specific reminder for the one item still missing on every return that is not entity-dependent. A request naming the exact document gets a faster response than a general "please send your remaining tax documents" note.

4. 4

   Reopen every entity-dependent file on September 16

   The day after the entity deadline, send the K-1 request to every client whose individual return depends on one. Do not wait to see who sends it unprompted.

5. 5

   Flag at-risk returns by September 30

   Any return still missing a document two weeks before October 15 needs a phone call, not another email. By this point the firm should already know exactly which returns fall into that group, because the checklist has been current since July.

6. 6

   File and archive with a complete record

   When a return is done, its full document set moves to a named client folder, not a scattered set of email threads. A signed engagement letter amendment or authorization needs the same tamper-evident record as any other signed document.

Chasing extension clients without starting over in September

The instinct after April is to set extended returns aside until closer to the deadline. That instinct is what turns a manageable July list into an unmanageable September one. Chasing extension clients works the same way chasing April clients does: name the specific missing item, send the request through a channel the client actually checks, and follow up on a fixed schedule instead of an ad hoc one.

Email alone struggles here for the same reason it struggles in April. A client searches their inbox for the most recent message from the firm and replies to a thread from March, or the request sits unread under forty other emails. A text with a direct link to upload gets read within the hour more often than an email does, particularly for clients who are not actively thinking about taxes in July.

How zendoc handles extension-season document collection

zendoc for accounting firms tracks each extended return as its own workflow instance, with the specific missing document as a named step rather than a general status. When a client’s K-1 depends on an entity return the firm also prepares, staff can hold that step until the entity deadline passes and reopen it automatically once September 15 has arrived, instead of relying on someone to remember which files need reopening.

The AI review reads each upload as it arrives and flags a K-1 with the wrong tax year or an unreadable scan before a preparer opens the file, the same way it does for a W-2 in April. zendoc does not sync with Drake, UltraTax, or Lacerte. Staff download the completed file set from zendoc and upload it to the firm’s tax software directly, a step that takes under a minute per client once every document is in.

For the base document set every individual return needs before it ever reaches extension, the tax document collection guide for CPAs covers the W-2 and 1099 side of the same process. zendoc for tax preparers covers the broader workflow across a full season.

Before and after

For the document checklist that covers a return from its first request through filing, or to join the waitlist, visit the zendoc homepage.

Sources:

• IRS: Oct. 15 deadline for extension filers is around the corner: confirms October 15 as a firm filing deadline, not an informal target
• IRS: About Form 7004: the automatic extension form for partnerships, S-corps, and other business entities
• AICPA National MAP Survey: accounting firm practice management benchmarks