If you are a consultant trying to make sense of your tax obligations, your business structure, and what records you actually need to keep, this guide covers the essentials without the jargon. You will find out where consultants typically go wrong, what HMRC expects, and what to do first.

Why accounting for consultants is different from generic small business advice

Consulting income does not behave like a shop or a trade. You might invoice a client in April for a project that runs through to July, take a large retainer upfront, or go months between engagements. That pattern creates specific tax questions that generic small business guides simply do not answer. According to the Office for National Statistics, professional, scientific and technical businesses make up 15.3% of all registered UK businesses, making it the largest single industry group. That means HMRC pays close attention to it.

Whether you operate as a sole trader or through a limited company, your structure determines which taxes apply, what you can claim, and how much you take home. Getting that wrong from the start is expensive to fix. The right choice depends on your turnover, your risk appetite, and whether IR35 is likely to apply to your engagements.

Where most consultants go wrong with their accounts

Most consultants who run into trouble with HMRC did not set out to cut corners. They simply did not know the rules that applied to them. These are the three areas where errors most commonly occur.

Treating all income as profit and not setting tax aside

When you invoice a client and the money lands in your account, it feels like yours. But 20% to 45% of it may belong to HMRC depending on your tax band. Consultants who spend without ringfencing tax regularly face penalties at self assessment time. HMRC can charge penalties if your return understates tax or misrepresents your liability, and those penalties stay with you personally even if an accountant files on your behalf.

Getting IR35 wrong when working through a limited company

If you provide services through your own limited company and a client could reasonably treat you as an employee, HMRC’s off-payroll working rules (IR35) require you to pay broadly the same Income Tax and National Insurance as an employee would. Since April 2021, medium and large private sector clients have been responsible for issuing a Status Determination Statement for each engagement. From April 2026, the threshold for who counts as a large or medium client has risen, as noted above. If you are unsure whether IR35 applies to a current or upcoming contract, this is not an area to guess.

What to do, in order

You do not need to have everything perfect before you start. You do need to follow the right sequence so you are not undoing decisions later at cost.

1. Step 1: Choose and register your business structure. Sole trader registration with HMRC is straightforward and free. Operating through a limited company offers liability protection and can be more tax-efficient above certain income levels, but it comes with additional filing obligations including annual accounts, corporation tax returns, and confirmation statements. If you are unsure which suits your situation, this is the single decision most worth getting right at the outset.
2. Step 2: Open a dedicated business bank account and keep it separate from your personal finances from day one. Every payment in and every expense out goes through that account. This makes bookkeeping accurate, makes VAT returns manageable, and gives HMRC a clean picture if they ever ask questions. Mixing business and personal finances is one of the most common and most avoidable sources of accountancy errors.
3. Step 3: Set up a simple record of your income and allowable expenses. For consultants, common allowable expenses include professional indemnity insurance, training and CPD directly related to your consultancy work, travel to client sites, home office costs (if you work from home), and software subscriptions used for client work. Keep receipts and log every transaction monthly, not at year end. Leaving it to the last minute means missing claims you were entitled to.

Once those foundations are in place, your accountant can handle your VAT returns if you are registered, your self assessment or corporation tax filing, and any payroll if you pay yourself a salary through a limited company. Everything after step three is filing and compliance, and that is where having someone on the end of the phone the same day makes a material difference.

Costs and what to expect

The honest comparison is not between paying an accountant and paying nothing. It is between paying an accountant and paying the combined cost of your time, your errors, and any penalties. Consultants billing at £60 to £150 per hour spend that same hourly rate every time they sit down to work out their tax position. At STZ Accounting, services are offered at fixed monthly fees with no tie-in. Sole trader packages start from £150 plus VAT per month and cover bookkeeping, bank reconciliation, VAT returns, annual accounts, and self assessment. Limited company packages start from £215 per month for turnover up to £100k and include corporation tax, confirmation statements, and payroll.

How to get started today

You do not need to have years of records in order or a fully formed plan before speaking to an accountant. The most useful first step is a clear conversation about where you are now and what your obligations actually are. David works with consultants across Scotland and the UK on a fully remote basis, with same-day responses and a fixed price agreed before any work starts.

• Check whether you are registered with HMRC correctly for your income type. If you are a sole trader earning above £1,000 per year, you must be registered for self assessment. If you operate through a limited company, corporation tax registration is separate and mandatory.
• Book a free call with David to confirm whether your current structure is tax-efficient and whether IR35 is a relevant consideration for your contracts. There is no obligation and no charge for the initial conversation.