Does a self-employed electrician, plumber or builder need a bookkeeper?

Bookkeeping and accountancy are two different jobs for a CIS subcontractor

From 6 April 2026, sole traders and partnerships with qualifying income above £50,000 must keep digital records and file quarterly updates under Making Tax Digital for Income Tax. The threshold drops to £30,000 from 6 April 2027 and £20,000 from 6 April 2028, which brings most full-time construction subcontractors into scope within three years. That single change is the reason the bookkeeper question is being asked far more often on site than it was two years ago.

Before answering it, separate the two jobs people tend to blur together. Bookkeeping is the ongoing recording of what happened: sales invoices, CIS payment and deduction statements, purchase receipts, bank transactions, mileage. Accountancy is the year-end judgement work: preparing the Self Assessment return, claiming capital allowances, calculating and recovering the CIS refund, and advising on structure.

The two are not interchangeable and they do not substitute for one another. A bookkeeper who records everything perfectly does not file the return that gets your money back. An accountant handed a carrier bag of receipts in January can still file, but the return will be slower, more expensive and less complete than one built on decent records. The realistic question is not "bookkeeper yes or no", it is "who does the monthly recording, and with what system".

Three complexity tiers: where your CIS business actually sits

Income is a weak test. A labour-only bricklayer earning £65,000 from one contractor has a simpler record than a £40,000 supply-and-fix electrician invoicing eleven customers with materials on every job. Complexity is what drives the workload, and it comes from four sources: number of income sources, whether you buy and invoice materials, VAT registration, and payroll.

Tier	Typical profile	Monthly bookkeeping load	Verdict
1. Single-contractor subbie	Labour-only, one or two contractors, no materials invoiced, not VAT registered, no employees	Under an hour: file the deduction statements, log mileage, photograph receipts	No bookkeeper. Software or a spreadsheet plus an accountant for the return
2. Multi-job trade with materials	Three or more contractors or direct customers, supply-and-fix work, often VAT registered, possibly above the MTD threshold	Three to six hours: invoice splitting, reverse charge decisions, supplier invoices, reconciliation, quarterly MTD updates	Borderline. Outsource if you are consistently behind, otherwise commit to a weekly routine in software
3. Small limited company with payroll	Limited company, PAYE scheme, own subcontractors or employees, CIS suffered reclaimed via EPS, VAT registered	Six hours or more: payroll, monthly EPS, CIS300 returns if you pay subcontractors, VAT returns, reconciliation	Yes, in-house or outsourced. The monthly deadlines are unforgiving

Most self-employed electricians, plumbers and builders reading this are in tier 1 or tier 2. The honest answer for tier 1 is that a bookkeeper is a luxury, and the budget is better spent on an accountant who knows the Construction Industry Scheme. If you are unsure what that specialism actually covers, our guide on what a CIS accountant does sets out the difference from a generalist.

What goes wrong without records: the missed refund and the 30% deduction

Two failures cost real money in construction, and both are record-keeping failures rather than tax-planning failures.

The shrunken refund. CIS deductions are taken at 20% on the labour element of every payment, before a single expense has been counted. Your actual liability, once mileage, tools, PPE, insurance and materials are included, is almost always lower, and the gap is the refund. Every expense you fail to record makes that gap smaller. The categories most often lost are the ones with no bank trail or no obvious receipt: cash purchases of consumables, small tools bought on the way to site, and above all mileage, which at 55p per mile for the first 10,000 business miles from 6 April 2026 is usually the largest single claim a subcontractor makes. HMRC expects a contemporaneous journey log, and a reconstruction from memory does not meet that standard. The full list of what you can claim is in our guide to allowable expenses for CIS subcontractors.

The missing deduction statements. Contractors must issue a payment and deduction statement within 14 days of the end of each tax month. Those statements are the evidence for the tax already paid on your behalf. Subcontractors who never file them end up rebuilding the year from bank credits, which understates the deduction whenever a contractor paid net of a retention or a materials adjustment. The claim then either understates what you are owed or triggers questions from HMRC. Duplicates can be requested, but chasing a contractor you finished with eighteen months ago is a slow business.

The 30% trap. The deduction rate is 20% for a registered subcontractor, 30% for an unregistered one and 0% under gross payment status. The 30% rate is not only for people who never registered. It also catches those whose details do not match when a contractor runs verification: a trading name change, a new UTR after incorporating, or a company number that does not tie back to the CIS registration. On £3,000 of monthly labour, the difference between 20% and 30% is £300 a month out of your cash flow, recoverable later but gone now. Keeping your registration details, UTR and company records straight and consistent across every contractor is a bookkeeping task, and it is why the record-keeping discipline matters even when the tax itself is simple.

In all three cases, note what the failure is not. It is not a missing bookkeeper. It is a missing habit.

The hybrid most subcontractors actually run: DIY records, professional return

The arrangement that works for the majority of tier 1 and tier 2 trades is straightforward. You do the recording as it happens, and an accountant does the year-end work.

In practice that means:

• Invoice from software or a template that shows labour and materials on separate lines, so the CIS deduction is applied to the labour element only
• File every payment and deduction statement the month it arrives, digitally or in one folder
• Photograph receipts the day you get them, tagged to the job
• Log mileage weekly, using an app if the manual log is not sticking
• Reconcile the bank once a month against the invoices you raised
• Hand it to an accountant who prepares the return, claims the capital allowances and pursues the refund

The reason this works is that the recording task in tier 1 is genuinely small, while the year-end task genuinely is not. Capital allowances on a van, the 24-month temporary workplace rule on subsistence, and the interaction between CIS deducted and the final liability are all judgement calls, not data entry. Our guide on how to claim a CIS tax refund walks through what that year-end process involves.

The hybrid stops working at the point where the monthly recording is no longer small, or where you keep not doing it. Being three months behind is the clearest signal there is. If you want to see where your figures land before deciding, our CIS refund estimator gives a working estimate from your gross income and deductions, and shows how much the expense side is worth to you.

When bookkeeping stops being optional: MTD, VAT and payroll triggers

Three specific obligations change the answer regardless of how organised you are.

Making Tax Digital for Income Tax. Above the qualifying income threshold, records must be kept digitally and quarterly updates filed through compatible software. The trap for construction is the definition of qualifying income: it is gross turnover before CIS deductions and before expenses. A subcontractor who banks £48,000 after 20% deductions on £60,000 of gross labour is measured on £60,000, so is in scope from April 2026, not out of it. For 2026/27 HMRC has said no penalty points apply for late quarterly updates in the first year, but late annual returns and late payment penalties still apply as normal. The mechanics are covered in our guide to MTD for Income Tax and CIS.

VAT and the domestic reverse charge. Once you are VAT registered and working on specified CIS services for another VAT and CIS registered business that is not an end user, the reverse charge applies and you invoice without charging VAT, stating that the customer accounts for it. Whether it applies is a per-invoice decision involving end-user status, the 5% de minimis and the zero-rating of new-build housing. That volume of judgement on every invoice is where most tier 2 trades concede that monthly help is worth it.

Payroll. If you employ anyone, real time information filings are due on or before every payday, and employer NIC is charged at 15% on earnings above £5,000 a year from April 2025. Payroll deadlines are monthly and unmovable, which does not sit well alongside a full week on site.

Limited company subcontractors: the threshold is lower

For a construction limited company, the case for structured monthly bookkeeping is stronger, and the reason is cash rather than compliance. A CIS-registered company reclaims the deductions suffered against its PAYE and NIC liabilities through the Employer Payment Summary each month, in real time, instead of waiting for the deduction to flow through a year-end return. That mechanism only works if the CIS suffered figure is accurate and submitted on time each month, so the recording has to happen anyway.

Add statutory accounts, a corporation tax return at 19% on profits up to £50,000 with marginal relief above that, dividends taxed at the 2026/27 rates of 10.75% basic and 35.75% higher, and a director's own Self Assessment, and the monthly discipline is no longer discretionary. The mechanics of the reclaim are set out in our guide to reclaiming CIS as a limited company. If you are still weighing the structure itself, CIS sole trader versus limited company covers the trade-offs, and the background to the scheme is in what the Construction Industry Scheme is.

Deciding: a short test for CIS subcontractors

Score one point for each of the following that is true of your trade business:

• You invoice three or more contractors or customers in a typical month
• You buy materials and invoice them on, so labour and materials must be split every time
• You are VAT registered
• Your gross income is above the current MTD for Income Tax threshold
• You run payroll, for employees or for yourself through a company
• You are currently more than one month behind on your records

Zero or one point: you do not need a bookkeeper, you need a repeatable monthly habit and an accountant for the return. Two or three points: it is a genuine judgement call, and the deciding factor is usually honest self-assessment of whether the habit is holding. Four or more: outsource it, either to a bookkeeper or as part of a monthly accountancy package, because the deadline count has passed the point where site work and admin can share the same week. What that costs is covered separately in our guide to bookkeeper costs for a self-employed tradesperson.

The decision is about complexity, not income, and for most single-trade subcontractors the answer is no bookkeeper and a firm monthly routine. What almost nobody in construction should do is skip both the records and the professional return, because that combination is precisely what turns an overpayment into money HMRC keeps. The records are yours to maintain, and the judgement calls are worth paying for.

If you want a straight view on which tier your business is in and what the monthly workload realistically looks like, our CIS accountancy services page sets out what ongoing support covers for subcontractors and construction limited companies.