SIC codes, chosen the way senior advisors choose them.

SIC stands for Standard Industrial Classification. The UK classification currently in use is UK SIC 2007, maintained by the Office for National Statistics and adopted unchanged by Companies House. It is a hierarchical taxonomy — 21 sections labelled A to U, then divisions, groups, classes and finally the five-digit code that appears on your company record. The five digits carry meaning: the first two identify the division, the third the group, the fourth the class and the fifth the UK-specific subclass.

What a SIC code is:

• A statistical classification of economic activity for the ONS and Eurostat.
• A summary field on the public Companies House register.
• A machine-readable signal for banks, EMIs, payment processors, insurers and lenders.
• An input into HMRC's compliance risk models and R&D claim credibility assessment.

What it is not:

• A legal authorisation. Filing a regulated SIC code does not grant any regulated permission.
• A tax rate. Corporation Tax and VAT are set by legislation, not by code.
• A commitment. It records what the company does today, not what it can ever do.
• Interchangeable with US NAICS or UK SIC 2003 codes. Do not reuse a code from a legacy document without re-mapping.

Companies House allows between one and four SIC codes on a company record. There is a persistent myth that filing all four gives the company 'more room to operate'. That is not what the field does. All four codes are read; there is no primary flag in the machine format; but every automated consumer of the record treats the first listed code as the primary activity. Founders who file four codes because they might one day expand into all four are unwittingly telling a bank that the company is already diversified — and diversification is a well-known money-laundering typology signal.

Our house rule:

• Single-activity businesses: file one code, the most specific fit.
• Genuinely two-line businesses: file two codes, primary first.
• Group-style holding companies: file the 64xxx holding company code first, then up to three real-activity codes if the parent itself trades.
• Never fill four codes 'to be safe'. It is the least safe choice available.

A separate category of SIC codes describes activities that require regulatory authorisation, sit inside anti-money laundering-supervised sectors, or match international sanctions typologies. Filing one of these codes on a company that does not hold the relevant permission is one of the few filings that will fail a UK bank application quickly and without appeal.

The rule is not 'avoid these codes'. Legitimate regulated businesses must file them. The rule is that filing them without the matching authorisation, or in the mistaken belief that the code sounds more impressive, is worse than filing nothing at all.

SIC codes are updated on the Confirmation Statement (CS01) — either at its normal annual due date, or by filing an early confirmation statement (there is no separate form). The fee is the standard confirmation statement fee. There is no penalty for changing a code and no minimum interval between changes.

What there is is a downstream consequence. UK banks receive an automated Companies House feed. A material change — for example, moving from consultancy (Section M) into regulated financial activity (Section K), or into a higher-risk retail category — commonly triggers a periodic review of an existing account. This is not a reason to leave an inaccurate code in place. It is a reason to make the change deliberately, alongside a short activity note the bank can attach to the file if it asks.

The wrong sequence is: change what the business does, ignore the SIC, get asked at the next bank review, and discover the record has been misaligned with the business for eighteen months. That single fact pattern is more damaging than the change itself would ever have been.

The exact process we run for every incorporation.

1. Write one sentence describing what the company actually does. Not the vision, not the pitch — the activity that generates the invoice. 'We sell branded athleisure to UK and EU consumers through Shopify and Amazon.' 'We build custom software for mid-market professional-services firms.' 'We provide strategy and operations advice to healthcare clinics.'
2. Identify the ONS section. Retail? Section G. Software? Section J. Professional advice? Section M. Property? Section L. This narrows the list from 700+ codes to roughly 30.
3. Descend to the group and read the description. Read the ONS explanatory note, not the code title. Descriptions often exclude activities the title suggests are included.
4. Prefer the most specific code available. Choose the residual '…n.e.c.' code only when no named code inside the group fits.
5. Sanity-check against the banking read. Ask whether a compliance officer, reading the code alone, would recognise the business you wrote in step 1. If not, revisit.
6. Confirm the code exists in UK SIC 2007. Not SIC 2003, not NAICS, not a bespoke description. Use the Companies House lookup on the filing form.
7. File one code unless the business genuinely has two revenue lines. Where two codes are truly needed, order them by revenue share.

That is the whole process. Five minutes, one page of notes, and a filing that supports every future application the company will make. Where the business is genuinely complex — multi-jurisdiction, regulated, or investor-facing — this is exactly the kind of decision our senior advisory team handles as part of a formation engagement rather than leaving to a form on a laptop at midnight.