When people ask us what is contractor accounting, the short answer is: it’s the financial infrastructure behind working for yourself as an independent professional. Invoicing clients, managing tax, handling payroll if you pay yourself a salary, registering for VAT, filing returns with HMRC and Companies House — all of that falls under the umbrella of contractor accounting.

The longer answer is that it’s more layered than most new contractors expect, and the decisions you make early on — particularly around your trading structure — shape everything that follows. We work with contractors across engineering, construction, IT, professional services, and consulting, and the same questions come up repeatedly. This post covers the foundations: what contractor accounting actually involves, how structure affects your obligations, and where things tend to go wrong.

Most UK contractors operate through one of two structures: their own limited company or an umbrella company. The choice shapes almost every aspect of your accounting, so it’s worth understanding what each involves before assuming one is automatically better.

With a limited company, you’re the director of your own business. You invoice clients through the company, pay yourself a combination of salary and dividends, manage corporation tax on company profits, handle VAT registration if your turnover exceeds the threshold (currently £90,000), and file annual accounts and a confirmation statement with Companies House. The administrative workload is real, but so is the tax efficiency — when the numbers work in your favour.

An umbrella company is a different arrangement altogether. You become an employee of the umbrella, submit timesheets, and receive a salary after PAYE deductions. The umbrella handles all the tax and National Insurance. There’s almost no accounting admin on your side, but you give up the flexibility and tax planning opportunities that come with running your own company.

The right structure depends on your IR35 position, how many clients you work with, how long your contracts typically run, and how much administrative responsibility you’re prepared to take on. There’s no universal answer — but there is usually a clearer answer once you look at the specifics of your situation.

IR35 — the off-payroll working rules — determines whether HMRC considers you to be effectively an employee, even when you’re technically contracting through your own limited company. If a contract falls inside IR35, the tax treatment changes: Income Tax and National Insurance are deducted at source rather than you taking dividends as a tax-efficient alternative to salary.

Since 2021, the responsibility for determining IR35 status shifted. Public sector clients and medium-to-large private sector clients now make the determination and must issue a Status Determination Statement. For smaller private sector clients, the contractor’s own intermediary (typically their limited company) still decides. This is a meaningful distinction because it affects where the liability sits if the determination is wrong.

We see contractors get into difficulty on IR35 in two ways. The first is ignoring the question entirely and assuming their contracts are outside IR35 without reviewing the actual working arrangements. The second is accepting an inside determination without pushing back, even when the working practices genuinely support an outside position. Both carry financial risk.

An IR35 review looks at the practical reality of how you work — substitution rights, control, and whether the engagement is genuinely project-based or functions like permanent employment. It’s worth getting right before you sign a contract, not after HMRC starts asking questions.

If you’re trading through a limited company, contractor accounting involves several moving parts running simultaneously throughout the year.

Bookkeeping and records

You need accurate records of all income and expenditure — invoices raised, expenses incurred, bank transactions reconciled. Cloud accounting software like Xero or QuickBooks Online makes this manageable, and many contractors run their bookkeeping in under an hour a month once the system is set up properly.

Salary and dividends

Most contractor directors pay themselves a modest salary (typically around the Secondary Threshold to avoid unnecessary National Insurance) and supplement it with dividends from company profits. This requires a payroll run each month, even if the salary amount is small, with RTI submissions to HMRC.

VAT

If your annual turnover exceeds £90,000, VAT registration is compulsory. Many contractors also use the Flat Rate Scheme, which can be administratively simpler and, depending on your sector, financially advantageous. VAT returns are typically quarterly under Making Tax Digital, meaning they must be submitted using compatible software.

Year-end obligations

At the end of each financial year, your company needs statutory accounts filed with Companies House and a Corporation Tax return (CT600) submitted to HMRC. These aren’t the same filing, and they often have different deadlines — missing either can result in automatic penalties.

In our experience, the contractors who find themselves with unexpected tax bills or HMRC penalties share a few common characteristics. They set up a limited company without fully understanding the ongoing obligations. They treat the company bank account as an extension of their personal finances. They defer bookkeeping until year-end, then hand over 12 months of unreconciled transactions to an accountant.

One situation we see more than you’d expect: contractors who wind down a limited company — or simply stop trading — without properly closing it or notifying HMRC. A dormant company that hasn’t been formally registered as dormant with HMRC is still expected to file returns. Failing to do so generates automatic penalties, and they accumulate quickly. We’ve seen contractors rack up well over £1,000 in fines on a company they considered finished with.

The other recurring issue is timing. Contractors who draw high dividends early in the year without accounting for corporation tax that will be due later can find themselves short when the bill arrives. Corporation Tax is paid nine months and one day after your company’s accounting year ends — it’s predictable, but only if you’ve been tracking your profits throughout the year rather than discovering them at year-end.

None of these are difficult problems to avoid with a basic system in place. But they’re surprisingly easy to stumble into without one.

We hear this question regularly, particularly from contractors who’ve just started out. The honest answer is: it depends on what you’re comparing it to.

A decent contractor accountant costs somewhere in the region of £100–£180 per month, depending on what’s included. That covers bookkeeping, payroll, VAT returns, year-end accounts, and corporation tax — the full compliance stack. Some firms price advisory work separately; others bundle it in.

What that fee buys you is not just the filing. It’s someone who knows the difference between an allowable business expense and something HMRC would challenge. It’s an IR35 review before you sign a contract. It’s timely reminders for every filing deadline. It’s someone who notices when your dividend drawings are outpacing your available retained profits.

The contractors who get the most from an accountant relationship are the ones who treat it as ongoing — asking questions in real time rather than once a year at filing season. A good accountant tells you things you didn’t know to ask about. That’s worth something that’s hard to put a number on, but the peace of mind and compliance confidence alone tend to justify the cost for most contractors we work with.

If you’re doing meaningful contract income through a limited company, DIY accounting is a false economy. The question is finding the right firm, not whether you need one.