01Verdict up front
The single strongest reason: this is a documented, recurring, money-linked pain (CIS deductions, reverse charge wording and statement chasing go wrong every time a subcontractor is paid), inside a category where incumbents visibly charge money, with a hard regulatory deadline (MTD for Income Tax and tightened CIS rules, both April 2026) forcing the buyer to adopt software.
02The idea as understood
Target market: UK construction subcontractors and small contractors (sole traders to roughly 20 staff) and the bookkeepers who serve them. Why now: Making Tax Digital expansion and continued HMRC CIS compliance pressure; generic invoicing tools mishandle CIS deductions and reverse charge VAT. Constraints: bootstrapped budget, low-contact validation, no artefact creation this run.
Gaps in the brief: no indicative price stated (prior internal research proposes £19 Solo / £29 Pro); no distribution asset stated; HMRC CIS300 filing scope unstated (prior research places recognised submission in "later", which this report adopts).
Prior work: this repository's opportunity reports (6 August 2026) already rank CIS-first invoicing first of ten UK opportunities at 8.0/10 "test first". Under the runbook's firewall they count as one INFERENCE signal and did not feed the factor scores; only externally checked evidence scored.
03Buyer and trigger
Buyer
The self-employed CIS subcontractor (electrician, plumber, plasterer, groundworker) paid by one or more contractors; secondarily the bookkeeper who tidies up after them.
Trigger
Raising an invoice for a contractor, and again when payment lands net of a 20% or 30% deduction. Split, deduction preview and reverse charge wording must be right at that moment.
Current workaround
Xero, QuickBooks or FreeAgent configured for CIS with varying success, or spreadsheets plus an accountant who reconstructs the position at year end.
Consequence
Disputed or delayed payment, VAT accounted for in error, unreconciled remittances, and missing statements that jeopardise the tax refund. HMRC now reissues statement information only by post.
04Evidence log
14 signals across vendor communities, professional press, incumbent pricing and HMRC/MTD sources. High confidence = page content confirmed directly. Medium = seen via search results only (several sites block automated fetching); dates on signals 1 to 4 are unverified and may pre-date the 24-month window.
| # | Source | Behaviour observed | Cost or spend | Date | Confidence |
|---|---|---|---|---|---|
| 1 | QuickBooks UK community thread | Subcontractor asking how to get a CIS payment and deduction report | Time chasing reports | Undated, flagged older | Medium |
| 2 | QuickBooks UK community thread | CIS set up but deductions not showing on the invoice; setup failure loop | Rework and support time | Undated, flagged older | Medium |
| 3 | MyICB Bookkeepers Forum thread | Bookkeeper unable to transpose CIS into Xero; support pointed to help files | Professional time | Undated, flagged | Medium |
| 4 | AccountingWEB thread | Accountant asking how CIS and MTD ITSA interact in Xero; unclear even to professionals | Professional time | 2025 to 2026 era | Medium |
| 5 | Tax Adviser (CIOT) article | Reverse charge pitfalls: suppliers account for VAT in error, customers recover in error | Incorrect VAT; assessment risk | Ongoing | High |
| 6 | ICAEW tax news article | HMRC stopped giving CIS statement details by phone; post only | Weeks of delay per statement | July 2024 | High |
| 7 | Tax Adviser (CIOT) guide | Statements are the subcontractor's first line of defence for reclaiming deductions | 20% to 30% of labour withheld per payment | Ongoing | High |
| 8 | Xero UK pricing page | CIS return filing sold as a paid add-on on top of base plans | ~£5/month add-on plus £7 to £65 plan | Current | High |
| 9 | FreeAgent page | £19 to £33 per month but free via NatWest, RBS, Ulster Bank, Mettle; handles CIS | £0 to £33/month | Current | High |
| 10 | Federation of Master Builders guidance | Tells sole trader builders to adopt software handling both CIS and MTD | Subscription plus setup time | 2025 to 2026 | High |
| 11 | GOV.UK / MTD guides collection | MTD ITSA mandatory April 2026 above £50k; quarterly updates; penalty points and £200 fines | ~£285 upfront then £115/year; £200 per missed deadline after 4 points | April 2026 mandate | High |
| 12 | Saffery (CIS reform) note | From 6 April 2026: monthly nil returns, fraud test, immediate gross-status removal | Penalties up to 30% of tax loss | Effective April 2026 | High |
| 13 | Heights Accountancy blog | Publishes step-by-step CIS screenshots for Xero/QBO/Sage because clients get it wrong | Accountancy fees for remedial setup | October 2025 | Medium |
| 14 | Prior internal research this repository, INFERENCE | Ranked the idea 8.0/10, first of ten; defined the £29 price test | £29/month proposed; 345 customers for £10k MRR | 6 August 2026 | Inference |
05Kill list
Disconfirming evidence was searched for deliberately, as the runbook requires.
| Finding against the idea | Seriousness |
|---|---|
| FreeAgent is free through NatWest, RBS, Ulster Bank and Mettle business banking and handles subcontractor CIS. A large share of the market can get a competent tool for £0. | High |
| The category is crowded, not vacant. QuickBooks includes CIS filing end to end; Xero, Sage, Zoho Books, Powered Now, Kletta and others advertise CIS features. The wedge must win on correct-by-default and remittance reconciliation. | High |
| Regulatory volatility. CIS rules change again in April 2026 and the MTD timetable has slipped before. Compliance-by-default carries a permanent rules-maintenance burden. (Also cuts the other way: it creates urgency.) | Medium |
| Willingness to pay may cap near £10/month against bank-bundled free tools; prior research pre-registers exactly this failure mode. (INFERENCE from prior synthesis.) | Medium |
| No corpses found. Searches for failed competitors in this niche found none (Albert acquired, Coconut pivoted, Powered Now active). Nobody has burned publicly here, but nobody has broken out either. | Low |
Searches that returned nothing usable: incumbent CIS-module churn rates; threads of buyers cancelling a dedicated CIS tool. Recorded as required.
06Competitor and incumbent map
| Option | Price | What buyers complain about |
|---|---|---|
| Xero + CIS add-on | £7 to £65/month plus £5 add-on | CIS setup hard to transpose; support points to help files; year-end adjustments |
| QuickBooks Online | £12 to £115/month, CIS included | Clunky or overkill; deductions not appearing despite setup; plan complexity |
| FreeAgent | £19 to £33/month, free via NatWest group banks | Invoice-first CIS workarounds historically; not a job-cost system |
| Sage / BrightPay | £16 to £115+ with add-ons | Capable but confusing for non-accountants |
| Trade apps (Powered Now, Tradify, Kletta, Joist) | ~£10 to £40/month | Optimise scheduling, not the "being paid" flow; not CIS/MTD-first |
| Do nothing / spreadsheet + accountant | Accountant fees; own time | No clean CIS export; year-end reconstruction; untenable under MTD quarterly updates |
07Score breakdown
| Factor | Weight | Score | Justification |
|---|---|---|---|
| Pain evidence | 25 | 2 | Complaints across four-plus channels, but fewer than ten dated within 12 months and costs rarely quantified by the speaker |
| Urgency | 20 | 2 | Pain recurs every invoice and April 2026 attaches penalties, but a sourced same-day cost for the subcontractor is inferred, not documented |
| Buyer reach | 20 | 2 | Named channels exist (trade forums, CIS-specialist accountants) but member counts and posting permissions are unverified |
| Manual pilot | 20 | 3 | Strong anchor met: correct invoice, DRC wording, remittance match and chase list are deliverable this week by hand |
| Price clue | 15 | 3 | Strong anchor met: documented incumbent spend that £19 to £29 undercuts or reframes |
08Proposed test design
Offer
"CIS correct before the invoice leaves your phone." A concierge pilot: right labour/materials split, deduction preview, reverse charge wording, and every payment reconciled against its statement. £29 per month (£19 sole trader), honestly positioned as done-with-you, not finished software.
Commitment action
Apply for the paid pilot and upload one recent contractor invoice plus the matching payment-and-deduction statement. The upload is the behavioural commitment; an application without documents does not count.
First channel
Two or three CIS-specialist accountants and bookkeepers asked to refer clients, backed by permitted posts in trade communities. Distribution itself stays a human action.
Gate rationale
Default gate adopted unchanged: the market is not unusually narrow. These thresholds are copied verbatim into the Phase 3 gate record before anything is published.
09Risks and unknowns
- Willingness to pay above roughly £10/month against free FreeAgent is unproven. This is the primary thing the test settles.
- Complaint recency is unverified on the strongest threads (fetches blocked); pain may be less acute in current software versions.
- Buyers may assume any CIS tool files CIS300 and MTD updates; a pilot without recognised submission may be rejected for that reason. The application form must probe this.
- Rules-maintenance burden and liability for compliance-by-default claims after April 2026 were not costed.
- The test will not settle: long-term retention, CAC below £100, or the RAMS companion thesis.
10Recommendation and next step
11Decision log
| Date | Decision | Decided by | Reason |
|---|---|---|---|