How your Companies House SIC code can affect an R&D tax relief claim (and why it matters)

If you’ve ever had an R&D tax relief claim pulled into a compliance check and thought “why us?”, one often-overlooked trigger is sitting in plain sight on the public record:

Your SIC code on Companies House.

A SIC code (Standard Industrial Classification) is meant to describe what your company does. HMRC can (and does) use available information to risk-assess claims, and a mismatch between your SIC code and the R&D story you’re telling can be enough to put your claim straight into the “needs a closer look” pile.

This blog explains what SIC codes are, how they interact with HMRC’s compliance approach, and what you should do before submitting a claim to reduce avoidable risk.

What is a SIC code?

When a UK company is incorporated, it selects one or more SIC codes to describe its main business activities. Those codes sit on the Companies House register and are updated (usually) via the annual confirmation statement.

Companies House themselves describe SIC codes as a way to classify your company’s business activities, and they explicitly note you can change them if they were wrong originally or your activities have changed.

Key point: SIC codes are not “tax” categories and they don’t determine whether you qualify for R&D. But they do shape how your company looks at first glance to anyone doing a desk-based review, including HMRC.

Why SIC codes can increase the chance of a compliance check

1) HMRC runs targeted compliance activity based on risk

HMRC’s published approach to R&D tax relief makes it clear they use targeted, proportionate compliance checks based on risk and behaviours. That matters because a SIC code is a quick “risk triage” data point: If your SIC code indicates a sector where HMRC doesn’t commonly see successful R&D claims, it can raise the perceived risk.

If your claim describes highly technical R&D but your SIC code suggests something unrelated (e.g., generic consultancy, retail, hospitality), it can look inconsistent, at least until explained. This doesn’t mean the claim is wrong. It means the claim may start the review under suspicion.

2) The new “additional information” requirement increases early scrutiny

For many claims, HMRC now requires an additional information form before you can claim. This is designed to help HMRC assess claims more efficiently and reduce error and abuse.

In practice, that means more claims are subjected to early, structured review. If your Companies House profile (including SIC codes) doesn’t “match” what’s in the additional information form and technical narrative, it can create friction immediately.

3) A mismatch can look like poor governance (even when the R&D is real)

HMRC compliance checks aren’t only about whether R&D happened. They’re also about whether: the company understands the rules, has kept proper records, and has taken reasonable care.

A SIC code that hasn’t been updated for years can be read as a signal that the company’s public-facing profile is not maintained, which may nudge a reviewer towards asking more questions.

What a “SIC mismatch” typically looks like in R&D claims

Here are common real-world patterns:

• Company pivots but SIC codes don’t change

Example: a business began as “general IT consultancy” but now builds proprietary software products and platforms, yet still shows a generic consultancy SIC.

• Group structures and multiple activities

A company may legitimately do both operational delivery and technical development, but only the operational SIC codes are listed.

• Legacy incorporation defaults

Many formation agents select broad SIC codes at incorporation and they never get revisited.

None of these make an R&D claim invalid, but they can make it harder to get approved smoothly.

Why getting the SIC code right is important (even though it’s not “the test”)

Because it helps you avoid avoidable problems:

• Fewer “easy” reasons for HMRC to open a check
• HMRC can still enquire, but you remove a simple inconsistency.
• Clearer positioning of your business activity
• If a reviewer sees “software development” or “engineering design” rather than a generic code, your R&D narrative starts from a more credible baseline.
• Better alignment across statutory and tax filings

Your CT600, accounts narrative, website, pitch decks, and Companies House record should tell a consistent story.

How to fix or update your SIC code (practically)

Companies House explains that you can update SIC codes when filing a confirmation statement, and if you need to change it sooner you can file an early confirmation statement. (companieshouse.blog.gov.uk)

Practical tips

Choose SIC codes that reflect your primary activities, not every minor sideline.

If your business genuinely has two core activities, it can be appropriate to list more than one SIC code (so long as they’re accurate).

Avoid “wishful thinking” codes (e.g., selecting “R&D” codes if you’re not actually an R&D service company). HMRC can spot that too.

“Will the right SIC code stop a compliance check?”

No. HMRC explicitly carries out targeted checks based on risk, and any claim can be selected. (GOV.UK)

But a correct SIC code reduces noise. It prevents your claim being pulled into a check simply because the public record makes the claim look odd at first glance.

Think of it as good claim hygiene:

It won’t guarantee a green light, but it avoids starting the process with an unforced error.

A quick pre-claim checklist (SIC focused)

Before submitting an R&D claim, do this:

• Check Companies House SIC codes
• Do they still represent what the company does today?
• Cross-check against your R&D narrative
• Would an outsider understand how a company with your SIC code could be undertaking the described R&D?
• Align other public indicators
• Website “About”, services pages, job ads, and announcements should broadly support the same commercial reality.
• Update SIC codes where needed (via confirmation statement)

Don’t leave it to chance, especially if you’re submitting a first-time claim.

Strengthen the technical justification

Even with perfect SIC codes, the claim must stand on the underlying R&D definition and evidence. The additional information form is a key part of that submission process.

Bottom line

Your SIC code won’t decide whether your work qualifies as R&D, but it can influence how quickly HMRC becomes sceptical and whether your claim gets pushed into a compliance check.

Keeping your Companies House SIC code accurate is a small admin job that can materially improve the “surface credibility” of your claim and reduce avoidable scrutiny, especially in a climate where HMRC is explicitly running targeted compliance activity.