Self Assessment document collection: an accountant's plan

What are the Self Assessment dates that matter now?

The 2025/26 tax year ran from 6 April 2025 to 5 April 2026. GOV.UK's deadlines page gives these dates, and they shape every step that follows.

Clients often forget that the January bill can include a first payment on account for the following year. Telling them early is one of the easiest ways to make a tax bill less of a shock, and it's a good reason to get figures to them before Christmas.

Why do generic document requests fail?

Most checklists online list everything a return could ever need. Send that to a client with one rental flat and they'll skim it, decide it's mostly irrelevant and put it aside. A list that says "here are the five things we need from you, based on last year" gets dealt with, as it feels like a short job.

The other problem is that records are often held by someone else. A P60 should be with the employee by 31 May, so it should exist, yet it may be buried in a work portal. Buy-to-let mortgage interest statements sit with the lender. Dividend vouchers may need to come from a platform. Clients stall because they don't know where to look, so tell them where each item usually comes from.

This is why it's worth building your requests from last year's return. The return tells you which income sources to expect, and any missing source becomes a sensible question: "Do you still own the flat in Leeds?"

How should you sort your clients?

Alphabetical lists and "biggest fee first" both miss the real issue, which is what's blocking each return. We use four groups, and you can sort most client lists in an afternoon.

Group D goes first because these clients eat your January. A phone call in November costs ten minutes, whereas their records landing on 28 January can cost you a weekend. New clients should also get an early call, as they won't yet know how you work.

What should your chasing schedule look like?

Here's a schedule that works back from the dates above, assuming you start this week. Keep the tone friendly, and make each message say exactly what's still missing rather than repeating the full list.

1. Week of 2 November: tailored request to all clients, with a date for records of 30 November.
2. 16 November: first reminder listing only what's outstanding.
3. 30 November: cut-off reminder, plus a phone call to group D.
4. 7 December: message about the tax code route for anyone it applies to, with a date for records of 11 December.
5. 4 January: firm message saying records received after your stated date may not be completed by 31 January.
6. 11 January: telephone round for anything open, with notes kept on the file.
7. 18 January: written notice to any clients at risk, explaining the penalties.

Whichever cut-off you choose, put it in writing, and say what happens afterwards. Clients who miss it can't then say nobody warned them. Check that your engagement letter supports the position you're taking, and speak to your professional body if you're unsure.

How many returns can your practice really finish?

This sum is rarely done, and it's the most useful thing you'll do this month. All of these figures are illustrative, so replace them with yours.

Say a practice has three staff working on returns for 20 hours a week each, leaving the rest for other work. From 2 November to 29 January is 13 weeks, minus one for Christmas, so 12 weeks. That's 3 × 20 × 12 = 720 hours.

Now the demand. There are 260 returns outstanding, at an average of 2.5 hours each including review, which comes to 650 hours. There's just 70 hours of slack, or 28 returns' worth.

That capacity isn't evenly spread. If 40% of records arrive in the last three weeks, that's 104 returns needing 260 hours, in a period when you have 180. You'd be 80 hours short, which means about 32 returns late or a lot of unpaid weekends. Moving just 15% of clients (39 returns, 97.5 hours) into December closes that gap. It's why the first request matters more than the last reminder.

What does a late return cost the client?

Having these figures ready makes reminders concrete. According to GOV.UK, the late filing penalty is £100 at first, even if no tax is due. After three months, daily penalties of £10 apply up to £900. After six months there's a further 5% of the tax due or £300, whichever is greater, and the same again after twelve months.

Late payment is charged separately: 5% of the unpaid tax at 30 days, six months and twelve months, plus interest.

Worked example

Take a client with £6,000 unpaid who files and pays seven months late (illustrative figures). The £100 initial penalty, £900 in daily penalties and a £300 six-month penalty come to £1,300 for filing, since 5% of £6,000 is also £300. Late payment adds 5% twice, or £600. That's £1,900 before interest. A client who sees that number in November is more likely to dig out the mortgage statement.

What records should you keep once the return is filed?

Collection doesn't end with submission. Self-employed clients must keep business records for at least five years after the 31 January deadline for the tax year, so the 2025/26 records must be kept until at least the end of January 2032 if filed on time. Other taxpayers generally have shorter periods, usually 22 months from the end of the tax year where the return is sent on time.

Agree what you're holding and for how long, and tell clients plainly that they're responsible for their own originals. Keep your retention period consistent with your data protection policy, and don't hold personal data longer than you've got a reason to. Rules differ for individual circumstances, so point clients to HMRC or a professional where needed.

Finally, spend one hour in February noting who was late and why. That list becomes next year's group D, and it's the most useful thing to carry forward.

What should a good document request say?

Long emails get saved for later, and later becomes January. Keep the first request short enough to read on a phone, and put everything specific to that client at the top. Here's a template you can adapt:

Hi Sam, it's time to gather your 2025/26 tax return records (6 April 2025 to 5 April 2026). Based on last year, we need: your P60 from your employer; a summary of rent and costs for the Leeds flat; your mortgage interest statement from your lender; and details of any new income or gifts to charity. Please send these by 30 November. That gives you your tax figure before Christmas, with time to plan for the 31 January payment.

There are three things to notice in this. It names the tax year in dates, because many clients don't know what 2025/26 means. It explains the benefit to them rather than your deadline pressures. And it ends with one clear date.

Add a catch-all question, as changes are what trip returns up: "Did anything change this year, such as a new job, a property sale, or income from abroad?" A client who sold shares won't necessarily think to mention it unless you ask. Treat a "no change" reply as useful information too, and note it on the file.

How Zaquil handles Self Assessment document collection

Here's how the plan above runs in Zaquil, from both sides of the desk.

• What the client sees: a branded secure portal with a short request list for their job. They upload what's asked for, complete an organiser or questionnaire, then approve and e-sign the return. Each item shows as done, so they can see what's left.
• What the firm sees: each return as a job built from a template, with a checklist, on a kanban board. Your four groups can be stages or job types, and anyone can see what's stuck and who owns it.
• Chasing: automations send the reminders and create phone tasks for group D when a date passes with records still missing, so your schedule keeps running in January when you're busiest.
• Deadlines: 30 December and 31 January sit against the job. Recurring jobs bring the return back next year.
• Replies and fees: email, chat, SMS, WhatsApp and calls come into one inbox against the client record, with AI drafts from your knowledge base for you to check. Fee invoices can be paid online, and you can lock a document until the invoice is paid.

Zaquil doesn't replace your tax software for filing with HMRC, so keep that for submission. See the accounting and tax setup and pricing: there's a 14-day free trial and no credit card needed to start, which is long enough to get November's requests out.