Is the 30% rule a legal requirement?

No. There's no UK law that sets a percentage.

How should a small business apply it?

Write it into a short AI policy: what AI can draft, and what a person must check. See do I need an AI policy?

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What is the 30% rule for AI?

Last checked: 17 October 2026 · The AI Till, UK

Short answer

The 30% rule for AI is an informal rule of thumb, not a law or official standard. Its usual meaning is that AI handles roughly 70% of a task, the repetitive drafting and sorting, while people keep the 30% that needs judgement, checking and accountability. Some people state it the other way round, so treat the number loosely.

A better way to use it

Rather than counting percentages, decide which steps must stay with a person:

Let AI do	Keep with a person
First drafts of emails and quotes	Prices, promises and anything sent to customers
Summaries of long documents	Decisions based on them
Sorting receipts and data	Tax returns and filings
Research and lists	Checking facts and sources

Why it matters in the UK

UK regulators expect a person to stay responsible. HMRC holds you responsible for your tax return, and the ICO expects human review for important automated decisions about people. See is AI regulated in the UK?

Other "30% rules"

You may also see a 30% threshold used in schools for how much of an essay can be AI-assisted. That's a local policy, not a national rule.

Sources

Checked 17 October 2026. Rules and prices change, so check the source before you rely on it. This is general information, not legal, tax or financial advice.

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