“Sorry, we’re full”: how small practices can say yes to MTD clients again

The quarterly work of Making Tax Digital for Income Tax is making small practices close their doors to new clients. This guide covers why that happens, what an MTD client actually costs you, and how a “self-file with oversight” service built on TaxNav and TaxNavHQ lets you take on new clients again without hiring.

7 min read · For UK accountancy firms

Two phone calls

Picture two phone calls in January 2027.

The first is from a landlord with £38,000 of rental income. HMRC has written to tell her she’s in Making Tax Digital for Income Tax from April. She’s always done her own return. Now she wants help, and she’s already been told “we’re full” by two firms.

The second is from a self-employed electrician on £45,000. Same letter, same panic, same answer.

Neither of them is a difficult client. Both would probably pay a sensible fee. Both will, in a few years’ time, be the kind of client every practice wants: a limited company, a VAT registration, a second property. And both are being turned away because, right now, a small practice can’t tell whether taking them on will cost it an hour a year or a day a quarter.

We wrote about the scale of this problem on AccountingWEB: Why 60% of small accountants are turning away new clients. This piece is the practical follow-up. It’s for the partner or practice manager who wants to stop saying no, and wants to know exactly how.

What “we’re full” really means

When a small practice says it’s full, it usually means one of two things.

“We can’t absorb the extra work.” This is the capacity problem, and it’s real. Practice Gateway estimates that around 60% of the self assessment process goes on communicating with clients rather than on the technical work. MTD for Income Tax takes that once-a-year chase and repeats it five times: four quarterly updates and a final declaration. At the same time, 59% of accountants told Wolters Kluwer that at least half of their income tax clients still aren’t using digital tools. And 48% of UK accountants told TaxCalc that a lack of capacity is already limiting their growth.

“We don’t know what it will cost us.” This is the uncertainty problem, and it’s the one people talk about less. MTD for Income Tax started in April 2026. The first quarterly updates were due on 7 August 2026. The first final declarations under the new rules aren’t due until 31 January 2028. So no practice has yet run a full MTD year for a client, from start to finish. Nobody has timesheet data. Nearly half of firms (47%, according to TaxCalc) plan to put their prices up for MTD clients, but very few can tell you by how much, or why.

When you can’t price the work, a new client stops looking like revenue and starts looking like risk. So the door closes.

The good news is that both problems have the same cause, and so the same fix. It’s not the tax that’s expensive. It’s the quarterly admin around it: the chasing, the follow-ups, the keying in. Take that out of your hands and both the capacity problem and the uncertainty problem shrink.

What an MTD client actually costs you

It helps to be specific. The table below sets out, roughly, what one quarter looks like for a typical sole trader or landlord under two ways of working. The timings are illustrative assumptions, not survey data. Replace them with your own as soon as you have a quarter or two of timesheets.

Multiply the left-hand column by four quarters and fifty clients and you can see why a two-partner firm says it’s full. Multiply the right-hand column by the same numbers and it’s a few days a year.

The other difference matters just as much: the right-hand column is predictable. You know what it costs, so you can price it. And once you can price it, you can say yes.

Three service levels, not one

The mistake many firms make is to offer MTD as a single full-service package, priced to cover the worst-case client. That’s too expensive for the landlord on £38,000 and still not profitable enough for the client with carrier bags of receipts.

A better approach is to split your in-scope clients into three groups.

The middle level is the one that changes your capacity. It lets you take on the clients you’d otherwise turn away, at a fee that works for both of you, because the quarterly work is theirs and the oversight is yours.

How it works for the client: TaxNav

TaxNav is HMRC-recognised bridging software built for sole traders and landlords. It’s designed for exactly the client who’d never sign up for full bookkeeping software.

• They keep their spreadsheet. Clients carry on recording income and expenses in the spreadsheet they already use, or start with a ready-made template. TaxNav links the spreadsheet to HMRC, which is how spreadsheet users meet the MTD digital records rules.
• They’re guided through it. Prompts walk the client through each quarterly update, so they don’t need to understand the legislation to file correctly.
• One licence covers everything. Self-employment, UK property and foreign property are all included, with no extra charges per property.
• The client pays. It costs £6 + VAT a month, or £60 + VAT a year. For a client who could never justify a full-service quarterly fee, it’s an easy yes.

For the client, MTD becomes a short job every quarter instead of a new system to learn. For you, there’s no data entry.

How it works for the practice: TaxNavHQ

TaxNavHQ is MyDocSafe’s practice dashboard, integrated with TaxNav. It’s where the “oversight” in self-file with oversight happens.

• Every client on one screen. See at a glance who has filed their quarterly update, who is running late and who needs a nudge. No spreadsheets of spreadsheets, no inbox searches.
• Chasing on autopilot. Tailored, automated reminders go out ahead of each deadline, so the 60% of effort that used to go on chasing is done for you. You step in only for the exceptions.
• Submit on the client’s behalf. If a client has entered their figures but forgotten to press submit, you can submit for them rather than chasing them again.
• Year end is already half done. When it’s time for the final declaration, the quarterly data is already there, ready for your adjustments, reliefs and advice.
• AI help across your client list. TaxNavHQ’s client AI agents work across your clients in parallel, looking into MTD issues, analysing them and fixing them, so your time goes on advice rather than admin.

Together, TaxNav and TaxNavHQ turn the quarterly cycle from something you do into something you watch.

A quarter under the new model

Here’s how the first quarter of the 2027/28 tax year might run for a self-file client.

1. 5 July: the quarter ends. The client has been recording income and expenses in their spreadsheet as usual.
2. Mid-July: TaxNavHQ sends an automated reminder. The client opens TaxNav, checks their figures and follows the prompts.
3. Late July: most clients have submitted. Your dashboard shows who hasn’t.
4. Early August: you check the exceptions. One client has entered the figures but not submitted, so you submit for them. Another has a query about a large expense, which takes you five minutes.
5. 7 August: the deadline passes. You spent minutes on the quarter, not days.

Repeat for November, February and May. When January comes, you start the final declaration with a year’s worth of quarterly data already in place.

Setting it up properly

A new service level needs to be written down, or it drifts back into full service. Four things to put in place:

1. The engagement letter. Add a short section for self-file clients explaining who does what. The client keeps digital records and submits their quarterly updates. The practice monitors progress, sends reminders, deals with queries within an agreed scope, and prepares the final declaration. Be clear about what happens if the client misses a deadline and wants you to take over, and what that costs.
2. A fixed quarterly fee. Price the oversight, not the hours. Because the work is predictable, a flat quarterly or annual fee works well, with full service as the clearly more expensive alternative.
3. A one-page client guide. How to set up TaxNav, how to link the spreadsheet, when the deadlines are, and who to contact with questions. A client who is well set up in the first quarter rarely needs chasing in the second.
4. A route back up. Some clients will struggle. Agree in advance when a self-file client should move to full service, and make that move easy.

Questions practices ask

“Won’t clients get their quarterly figures wrong?”

Some will. But quarterly updates are cumulative, year-to-date figures, so mistakes can be put right in the next update or at the final declaration, which is where your review adds the most value. Your oversight catches problems early, and your year-end work puts them right.

“Am I giving away fees?”

You’re giving away low-margin work. Chasing and keying in figures is the work clients value least and resent paying for. Year end, planning and advice are where the relationship and the margin are, and you keep all of that.

“What about clients who just won’t use software?”

They stay on full service, priced accordingly. Self-file with oversight isn’t for everyone. It’s for the clients you’d otherwise have to turn away, and for existing clients who’d rather do it themselves for a lower fee.

“Do I need to be ready for all of this before April 2027?”

No. Start by moving a handful of your most organised clients onto the self-file level now, while the first cohort is still in its first year. By the time the £30,000 cohort arrives, you’ll have real timesheet data and a service you know works.

Your 90-day plan before the April 2027 cohort

Days 1 to 30: segment. HMRC will use 2025/26 returns to identify who’s in scope from April 2027. Go through your self assessment list and put everyone with qualifying income over £30,000 into one of the three service levels. Our free MTD client segmentation tool can help with the first pass.

Days 31 to 60: build the service. Write the engagement letter wording, set the fee, create the one-page client guide and set up TaxNavHQ.

Days 61 to 90: pilot, then open the door. Move five to ten organised clients onto the self-file level and watch a quarter through the dashboard. Then change what you say when a new enquiry comes in. Instead of “Sorry, we’re full,” say “Here’s how we can help.”

The bottom line

The practices that come out of MTD strongest won’t be the ones that hired fastest or closed their doors earliest. They’ll be the ones that worked out what the quarterly work really costs, made it small, and built a service around it.

The next time a landlord on £38,000 calls, you won’t need to say you’re full.

Sources: Practice Gateway research, cited in AccountingWEB, “MTD for Income Tax: the capacity question firms cannot afford to ignore”, May 2026. Wolters Kluwer, MTD in practice (100 UK accountants), 2026. TaxCalc survey of 215 UK accountancy professionals, autumn 2025, and unrepresented-business analysis, February 2026. GOV.UK guidance on MTD for Income Tax thresholds and deadlines. TaxNav pricing: taxnav.digital/pricing. Timings in the cost table are illustrative assumptions.