Triage MTD quarterly filings for UK accountants
One screen, every client, every quarter
Executive Summary
In a nutshell
A workflow co-pilot built for the agent, not the end client. UK accountancy firms now face four quarterly updates plus a final declaration per affected client (a five-fold submission increase) since MTD for Income Tax went live on 6 April 2026. Every MTD-recognised tool on HMRC's list is a client-facing bookkeeping product: Xero, FreeAgent, Coconut, untied, TaxNav. None give a sole practitioner one screen to triage 80 clients before the 7 August deadline. Build the layer that sits above the bookkeeping ledgers and turns 80 separate file-and-pray sessions into one batched, reviewable, auditable run.
The Story
Meet the user
Marcus runs a four-person practice in Shrewsbury. He has 96 sole-trader and landlord clients above the £50k threshold. Until last month his job was simple: chase records once a year, file a self-assessment, invoice. From 6 April 2026 that's gone. Now every one of those 96 clients owes HMRC a quarterly update by 7 August, then 7 November, then 7 February, then a final declaration plus the legacy 25/26 self-assessment in the same window. Five touchpoints per client, 480 filings a year where there used to be 96. His junior is on holiday. His software is Xero for some, FreeAgent for others, spreadsheets for the builders, and a shoebox of receipts for one farmer who refuses to budge.
Marcus opens his practice management dashboard. It tells him client status. It does not tell him whose Q1 figures are missing, whose ledger doesn't tie, who hasn't approved, whose HMRC submission failed last attempt, or which 14 clients he can batch-file in the next hour. He's quoted Karbon at £4,000 a year and IRIS at more, and they still won't do the bit he actually needs, the bit between "client data exists somewhere" and "submission accepted by HMRC". Then he discovers Quarterli: a single screen showing all 96 clients as a triage queue, colour-coded by readiness, with batch submission via the agent services account and an audit trail he can hand to his PII insurer.
Scores
How does this idea stack up?
7.6/10
Around 35,000 UK accountancy firms, low hundreds of millions £ in addressable spend, and a clear gap (no agent-first quarterly co-pilot exists).
81% of UK accountants name MTD as their single biggest operational challenge. AccountingWeb headlines openly call it "panic" and "a question of capacity".
HMRC MTD ITSA APIs are public and documented. Solo-buildable in 4-6 weeks, plus a recognition cycle. Not trivial: agent services account OAuth and multi-tenant audit trails.
Mandate live 32 days ago. First quarterly deadline 7 August 2026, so 91 days out at time of writing. Search volume on key terms tripled in March 2026.
Demand is structural (quarterly forever), but the gap is transitional. Incumbents (Xero, IRIS, TaxCalc, Bright) will close it over 3-5 years. Build for a profitable window, not an empire.
Moderate. HMRC recognition cycle, agent OAuth, multi-tenant data, GDPR, B2B sales cycle. £300-£800 to launch, 2-3 month runway before meaningful revenue.
Strongest
Timing
Genuinely a compliance before/after with three months until the first deadline.
Watch out
Durability
This is a 3-5 year window not a forever business. Plan an exit, an acquihire path, or a feature pivot from day one.
Pain Point
The problem
“MTD doesn't create a new burden, it exposes an existing shortfall, and there's no clear plan for who is going to do the extra work.”
— AccountingWeb thread on practice capacity, May 2026
The MTD ITSA mandate landed on 6 April 2026 for sole traders and landlords with qualifying income above £50,000. Each affected client now owes HMRC five separate filings per year (four cumulative quarterly updates plus a final declaration), where they previously owed one annual self-assessment. For accountancy practices the maths is brutal: a firm with 100 affected clients goes from 100 annual filings to 500. Headcount doesn't scale that way. The Accountex headline of 1 May 2026, "MTD is a labour problem, not a software problem", captures the consensus.
The acute, recurring complaint across AccountingWeb, ICAEW guidance, and Tax Adviser is not "we don't have software". It's "we don't have an agent-facing workflow". Existing MTD-recognised products (Xero, FreeAgent, QuickBooks, Coconut, untied, TaxNav, Sage) are bookkeeping ledgers built for the end client. They each handle one client beautifully. None handle 80 clients in triage. ICAEW data shows 59% of accountants report at least half their clients are non-digital, so the agent has to chase, transcribe, reconcile, review and submit, five times a year, across heterogeneous client systems. The practice management category (TaxDome, Karbon, IRIS, Bright, Capium, Accountancy Manager) is closer but still pitched as horizontal client management, not vertical MTD batching.
The threshold drops to £30,000 on 6 April 2027, doubling the affected population, and to £20,000 on 6 April 2028, tripling it again. The pain compounds.
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