How the data is built
How the numbers on this site are produced, in enough detail to check them, including the parts that are guesses and the parts that can be wrong.
Where the data comes from
One source: the Home Office Register of licensed sponsors (workers), published on GOV.UK under the Open Government Licence. Company details come from the Companies House monthly data snapshot, also open data.
Nothing is scraped from job boards, bought from a broker, or entered by hand. There are currently 127,701 employers on the register.
How often it updates
The register is re-downloaded once a day. GOV.UK does not publish at weekends or on bank holidays, so a day with no changes is normal and not a failure. The Companies House snapshot is monthly, so company details can be up to five weeks behind.
Every page shows the timestamp of the data it is built from. If that date looks stale, it is: something has broken and you should check GOV.UK directly.
How employers are identified
An employer is identified by name plus town, not name alone. Chains and franchises repeat one name across many towns, and treating those as a single employer would hide real additions and removals.
The consequence is worth knowing: if an employer moves town, or the register changes how its town is spelled, it can look like one employer left and a different one arrived. That is a limitation of the source, not something we can fix from outside it.
Industry tags are our guess, not official data
The official register contains no industry field. The tags on this site are produced by keyword rules over the employer's name, so "Riverside Nursing Home" becomes Healthcare & Care.
About 12% of employers end up in "Other", because their name carries no clue about what they do. They are there to make searching possible, and they are wrong often enough that you should not rely on them for anything that matters. Always confirm with the employer.
Companies House warnings, and how they can be wrong
Employers are matched to Companies House by normalised name: case, punctuation and legal suffixes are standardised, so "The Foo Company Limited" and "FOO CO LTD" match. Different legal forms are kept apart, because "Foo Ltd" and "Foo LLP" are different companies. Previous company names are matched too, since the register is slow to follow a rename.
This is a name match. It is not an official link, and it is the weakest step in the pipeline. Two things follow from that:
- A warning is not proof. Every warning links to the Companies House record so you can check it yourself rather than take our word for it.
- No warning does not mean vetted. Roughly a third of employers on the register are not limited companies at all. Councils, NHS trusts, schools, universities and charities have no Companies House record to check.
Where one normalised name is held by more than one company and we cannot tell which is the employer, we show no warning at all. Dissolving a company frees its name, so a live employer often shares a name with a dead company, and picking the wrong one would tell somebody their prospective employer was being wound up when it is trading normally. If exactly one of the two is active we use that one, because a dissolved company cannot hold a sponsor licence. Otherwise we say nothing.
The warnings are not equally serious, which is why each one says what it found rather than just turning red. A company in liquidation is grave. Accounts filed late is often paperwork at a company trading perfectly well. A company incorporated within the last 365 days is not a problem at all, only unusual enough to mention.
Damaged characters in the source
The official CSV contains employer names that were already broken before publication: an apostrophe arrives as a byte that cannot be decoded, so a real employer appears with question marks in the middle of its name. The bytes needed to recover them were destroyed upstream, so nobody can restore them, including us.
We repair only the specific damaged shapes we have actually observed, and nothing else. Guessing at the rest would mean renaming an employer to something it is not called, which is worse than showing the damage.
What stops bad data being published
The pipeline runs unattended and publishes straight to this site, so it refuses to publish figures that look implausible. It stops if fewer than 10,000 employers are parsed, or if the register moves by more than 10% in a single run. Real daily movement is a fraction of a percent, so anything near that limit is far more likely to be a broken download than news.
On a refusal nothing is written, the old data stays up, and the job fails loudly so a human looks at it. The site going a day stale is a much smaller problem than the site going confidently wrong.
The change history
GOV.UK publishes who holds a licence today. It never publishes who stopped. So every day's register is compared with the previous day's, and the differences are recorded permanently.
The change log shows the last 30 days, and the homepage highlights the last 7. The full record goes back to when the pipeline started and is never deleted, which is what makes it possible to answer when an employer first appeared, how long it held a licence, and which sectors are growing.
One honest limit: an employer already on the register the first time we looked has no recorded start date. All we can say is "on or before" the day we started watching, and anywhere that date is used it says which of the two it is.
What this cannot tell you
- Whether an employer is hiring. A licence is a permission, not a vacancy.
- Whether they will sponsor you. That is their decision, and it depends on the role and the salary rules.
- Why an employer left the register. Licences lapse, get surrendered, get revoked, and companies close. The register does not say which, so neither do we.
- Anything about your own eligibility. That is regulated advice and this is a search box.
Check our work
Everything the site displays is published as plain JSON on the data page, free and with no account. If you think a number here is wrong, you can download the same files and recompute it. If you find a mistake, tell me at hello@knowyoursponsor.co.uk.
Last updated 11 September 2026.