The Best CIS Accounting App for
UK Subcontractors

CIS makes construction one of the few trades where the tax system takes its cut before you even see the money. Every time a contractor pays you, they hold back 20% of your labour (30% if you are not registered) and send it to HMRC. By the time your Self Assessment is worked out, you have usually overpaid, and you are owed a refund. The right app is the one that captures every deduction and every allowable expense so that refund is as large, and as easy to claim, as it should be.

What a CIS subcontractor actually needs from an app

CIS is not like ordinary self-employment. A graphic designer or a consultant is taxed on profit at the end of the year and pays in one go. A construction subcontractor has tax skimmed off at source on every payment, then reconciles at Self Assessment. That single difference reshapes what good software has to do.

In practice, the app you choose has to do three things well. First, it must total your CIS deductions accurately across every contractor you worked for, because that figure is the tax you have already paid. Second, it must capture every allowable expense, because tools, fuel and insurance directly increase your refund. Third, it must produce a Self Assessment, or feed clean numbers into one, because that is where the deductions and expenses finally meet.

You can sanity-check your own position before choosing anything. The CIS tax refund calculator estimates what you are likely to get back from your deductions and income, and it is worth running a check on your tax code too, since a wrong code can quietly hold back money that should be sitting in your refund.

The contenders, compared honestly

There is no single "best" app for every subcontractor. The right choice depends on whether you want free filing, human help, or the cheapest possible automated bookkeeping. Here is where the main options genuinely sit.

A few honest notes on that table. Pie's free Self Assessment filing is a real advantage, and it is built around the SA100 plus supplementary pages including rental and dividend income, with paid extras such as a return check around £59.99 or a done-for-you return around £149. It earned "Best Tax App UK 2025" recognition, and if your situation is straightforward, the price is hard to argue with.

Kletta is the premium option, Finnish-built and HMRC-recognised, with a human UK bookkeeper and a Self Assessment review on its paid tiers. It explicitly covers CIS, property income and capital allowances, and runs a two-sided accountant channel. If your books are chaotic, or you simply do not want to touch them, paying £19 to £49 a month for someone to sort it is a legitimate trade.

TapTax is the low-cost, automation-first choice. It is freemium at £0, £4.99 and £9.99 a month, with open-banking auto-import, AI categorisation, receipt scanning and mileage, all behind a one-tap "Tap. File. Done." flow. It is built for Making Tax Digital and is MTD-compatible, but its HMRC production recognition is still pending, so today it shines as the cheapest way to keep accurate, refund-ready records rather than as your sole filing route.

Where TapTax genuinely wins, and where it does not

It is only fair to be specific. TapTax wins on price: a free tier and a £4.99 paid tier undercut Kletta's £19 floor by a wide margin, and unlike Pie's paid add-ons, the core bookkeeping costs nothing to start. It wins on automation, because open-banking import plus AI categorisation means your contractor payments and expenses land and sort themselves with almost no manual entry, which matters when you are on site all day. And it wins on simplicity, because the whole app is oriented around getting to a filing, not around invoicing modules or payroll you will never use.

Where it does not win, today, is recognition and human support. Pie and Kletta can file direct to HMRC right now; TapTax's recognition is pending, so it is best paired with a recognised filing route until that lands. And Kletta's human bookkeeper is something no software-only tool replicates. If you want a person to check your CIS return, Kletta has the edge.

The expenses that grow your CIS refund

Because CIS deductions are taken on your labour before expenses, every allowable cost you record reduces taxable profit and pulls more of that deducted tax back to you. The common, defensible claims for construction subcontractors are tools and equipment, protective clothing and PPE, business mileage at 45p per mile for the first 10,000 miles, materials you funded, public liability insurance, mobile phone, and a fair proportion of home-as-office admin costs.

This is exactly where automated capture earns its keep. A receipt for a £180 cordless drill or a tank of diesel on the way to a temporary site is worth real money at the margin, and the apps that scan receipts and import bank transactions lose far fewer of them than a shoebox ever did. If your work mixes site labour with other income, the sole trader tax calculator helps you see how expenses, the £12,570 personal allowance and Class 4 National Insurance at 6% combine to set your final bill, and therefore your refund.

MTD changes the calculation from April 2026

The biggest reason to pick your app deliberately now, rather than later, is Making Tax Digital. From April 2026, MTD for Income Tax is mandatory where combined self-employment and property income exceeds £50,000 of gross income. It extends to above £30,000 from April 2027 and above £20,000 from April 2028. Crucially, the test is on gross turnover, not profit, so a subcontractor invoicing £55,000 of labour and materials is in scope even if expenses bring taxable profit well below that.

Under MTD you keep digital records and send quarterly updates to HMRC instead of a single annual return. That suits CIS workers reasonably well, because the deductions and expenses you should already be tracking each quarter are exactly what the updates report. The plain-English MTD guide for sole traders sets out the timeline, the penalty regime and what each submission has to contain. The practical point is simple: an app that already imports your bank feed and categorises spend turns quarterly filing into a review rather than a scramble. A spreadsheet does not.

Who should pick what

If you want the cheapest possible accurate bookkeeping, with your contractor payments and tool receipts captured automatically and your CIS deductions tracked all year, TapTax's free or £4.99 tier is the most cost-effective starting point, and it is built for the MTD world you are about to enter. If you want a recognised tool that files your Self Assessment free today and your affairs are simple, Pie is an excellent, genuinely free option. If your records are a mess, or you would rather a human handled the CIS return entirely, Kletta's £19 to £49 tiers buy you a UK bookkeeper and a reviewed return.

Heavier accounting platforms such as FreeAgent, QuickBooks Self-Employed and Coconut can also handle CIS, but they are broader, generally pricier or bank-bundled, and most subcontractors do not need that weight. For a one-person trade where the whole game is maximising a refund and meeting MTD cleanly, lighter and cheaper usually wins.

People also ask

Whichever you choose, the principle holds: capture every deduction, claim every genuine expense, and be ready for quarterly MTD. TapTax does that for free to start, connects to your bank, and is built for Making Tax Digital, so you can keep refund-ready records without paying a penny until you are sure. Tap. File. Done.