Accuracy
Every tool of this kind says it is accurate. This page says what Tarn.hr actually does to be accurate, what that has caught so far and what it still does not prove.
Where your data lives and who touches it is a different question, answered on the security page.
15
Situations, each with its own written statement of current law
16
Primary sources behind them, each dated the day it was read
10
Out of date answers the eval watches for
Guidance last checked against primary sources on 9th November 2026. That date is one constant in the codebase. It is what the footer of every page prints, it is what this page prints and it is what the build measures against, so there is no version of it that can be older than it looks.
A general AI tool answers an employment law question out of whatever it absorbed in training, which is a mixture of the law as it stands, the law as it used to stand and confident guesswork. It has no way to tell you which it reached for.
Each of the 15 situations Tarn.hr handles carries its own statement of the law that applies to it, written by hand, checked against the primary sources listed below. That statement goes into the request, and the guidance is written from it. It is the difference between asking somebody to recall the law and handing them the law before they start.
This is also why the product refuses to state a pending change in the present tense. Several of the rules that matter most to a UK employer right now are announced rather than in force, and the two are a year apart.
The changes to UK employment law that Tarn.hr already knows about and that will change something it says. Each is recorded in the code against the situations and policies it touches, and once a dated change arrives the build fails until those briefings have been read again. Until then they are written as coming, not as in force.
1st January 2027
Date fixed in law
The qualifying period for unfair dismissal will fall from two years to six months, and the cap on the compensatory award will be removed. Source
Date to be set
No date fixed
Dismissing someone in order to impose changes to pay, hours, pensions, time off or certain shift patterns is expected to become automatically unfair in March 2027, with no day set and the regulations to bring it in not yet made. Source
Date to be set
No date fixed
A new Acas Code of Practice on disciplinary and grievance procedures is to replace the 2015 Code. Acas expects it to take effect in 2027. Source
Date to be set
No date fixed
Clauses that stop someone speaking about harassment or discrimination are to become void. The regulations are expected in September 2027. Source
Date to be set
No date fixed
A second trigger for collective redundancy consultation, counted across the whole organisation, is to be added at a threshold not yet set. Expected in April 2027. Source
Date to be set
No date fixed
Pregnant employees, and those in the six months after returning from family leave, are to get stronger protection from dismissal. Expected in October 2027, with no day set. Source
Date to be set
No date fixed
An employer refusing a flexible working request will have to rely on one of the statutory reasons and explain why refusing is reasonable. Expected in October 2027. Source
Date to be set
No date fixed
A right from the first day of employment to up to two weeks of unpaid bereavement leave, including after a pregnancy loss before 24 weeks, expected from April 2027. Source
Date to be set
No date fixed
Offers of guaranteed hours, reasonable notice of shifts and pay for shifts cancelled or cut short. No date has been set: the government will set the timing after consultation. Source
Date to be set
No date fixed
Menopause and gender pay gap action plans are to become compulsory for employers with 250 or more staff, expected in March 2027 for public authorities and April 2027 for everyone else. Source
Every statute, set of regulations and statutory code the briefings lean on, with the day its page was last opened and read against the prose. The links go to the publisher rather than to anybody’s summary of it, so you can check the wording yourself.
Read 4th October 2026
Unfair dismissal, the right to be accompanied's statutory backdrop, statutory sick pay's parent provisions, and redundancy as a fair reason for dismissal. Also section 86, the minimum notice bands behind lib/tools/notice-period.ts: a week from one month, a week per complete year, twelve weeks at the top, and nothing at all below a month. Section 86 was re-read on 4th October 2026 and carries no prospective amendment, so the notice bands are unaffected by the 2025 Act.
Read 30th August 2026
The 2026 and 2027 changes the scenarios turn on: day-one statutory sick pay, the doubled protective award, sexual harassment as a qualifying disclosure, and the unfair dismissal qualifying period dropping to six months.
Read 22nd October 2026
Protected characteristics, harassment, discrimination arising from disability, and the duty to make reasonable adjustments. Sections 40 and 40A were re-read on 22nd October 2026 for the harassment changes: legislation.gov.uk then showed section 40(1A) to (1C) and the word inserted into section 40A(1) as changes not yet applied, both by the 2025 Act.
Read 28th September 2026
The statutory right to be accompanied at disciplinary and grievance hearings. Section 10 also carries the only fixed period the Acas Code contains, the five working days within which a postponement for an unavailable companion must fall, and section 13 defines a working day as excluding weekends, Christmas Day, Good Friday and bank holidays.
Read 30th August 2026
Whistleblowing: what makes a disclosure qualifying and protected, and detriment and dismissal for having made one.
Read 30th August 2026
TUPE transfers: what transfers, the duty to inform and consult, and dismissals connected with a transfer.
Read 28th September 2026
Disciplinary and grievance procedure, what the Code does and does not apply to, and the tribunal uplift for unreasonably failing to follow it. lib/tools/disciplinary-timetable.ts leans on it for which steps are required, and for the fact that it sets no timescale for any of them beyond promptness and no unreasonable delay.
These change without the law changing, which makes them the ones most likely to go stale while still reading as correct. The April rates pages are the first to be re-read each year.
Read 12th October 2026
The instrument that moved the employment tribunal time limit from three months to six. Made 1st September 2026, in force 1st October 2026. Regulation 3 commences section 152 and Schedule 12; regulation 4 carries the transitional rule, so six months applies only where the relevant date falls on or after 1st October 2026 and anything earlier keeps three months minus one day. Its Schedule, table 2, fixes the relevant date for the TUPE complaints: the date of the transfer for employee liability information (regulation 12), and the date the transfer is completed for informing and consulting (regulation 15). Schedule 12 to the Act, paragraph 13, changes both limits from three months to six. Read this before writing anything about the limit, because both figures are correct for different facts.
Read 9th November 2026
The instrument that takes contract claims in Scotland from three months to six. SSI 2026/327, made 3rd November 2026 after the Scottish Parliament approved the draft, in force 9th November 2026. Article 2 substitutes six for three in article 7(a) and (b) of the 1994 Scottish order. Article 3 applies it only where the effective date of termination, or where there is none the last day worked, is on or after 9th November 2026, so a Scottish contract claim where employment ended before then keeps three months minus one day. Re-read on 9th November 2026, the day it came into force: shown only as originally made, with no amendment.
Read 9th November 2026
Acas's own running list of what has commenced and when, which is the quickest way to answer 'is this in force yet?'. Confirms the 6th April 2026 tranche, electronic balloting on 25th August 2026, the time limit on 1st October 2026, the harassment duty on 30th October 2026, and Scottish contract claims on 9th November 2026. Read on 22nd October 2026, when it had last been updated on 20th October. Re-read on 9th November 2026, last updated 30th October: the Scottish change still listed for 9th November, and an Acas consultation on flexible working requests open until 17th December 2026, which changes no law.
Read 22nd October 2026
Eligibility, the 28 week limit, fit notes and form SSP1.
Read 22nd October 2026
The statutory sick pay rate the absence scenario quotes: the lower of £123.25 a week or 80 per cent of average weekly earnings. This page is superseded every April, so it is the first one to re-read.
Read 22nd October 2026
Statutory redundancy pay: who qualifies, how it is calculated, and the caps. Also the two figures lib/tools/redundancy-cost.ts is built on, the £751 cap on a week's pay and the £22,530 maximum, both in force from 6th April 2026. Revised every April, so this is the first page to re-read.
Read 22nd October 2026
The second source for the statutory notice bands, agreeing with section 86 exactly: one week from a month to two years, a week per year to twelve, then twelve weeks. Also that a contract may give more notice than the statute and may not give less.
Read 9th November 2026
Which measures are in force and which are only announced. The scenarios are careful never to state a pending change in the present tense, and this is the page that settles what is pending. It is not sufficient on its own: it did not list the tribunal time limit under October 2026, which the commencement regulations above had already brought into force, so read both. Updated 22nd October 2026, moving fire and rehire from January to March 2027. Re-read on 1st November 2026: fire and rehire still under March 2027, and breach of contract claims in Scotland listed for 9th November 2026, later than the rest of the time limit change. Updated again on 5th November 2026 and re-read on 9th November: every month it gives for a measure Tarn covers is unchanged, and it adds seafarer regulations on 1st December 2026, which Tarn does not cover.
Read 22nd October 2026
The instrument behind the harassment changes. Made 1st October 2026. Regulation 3 brings section 20 (all reasonable steps to prevent sexual harassment), section 21 (harassment by third parties) and section 22 (the power to make provision about reasonable steps) into force on 30th October 2026, alongside trade union measures. Its transitional and saving provisions, regulations 4 to 8, concern only the trade union measures and say nothing about sections 20 to 22.
None of these is a review process that somebody has to remember to run. They are automated checks, they run on every proposed change and a failure stops the change reaching the site.
Wordings that were wrong, or that were right until the law moved, are held in a list. Any of them reappearing in the briefings fails the build. This exists because a correction was once applied to one of the two files carrying the law and never carried across to the other, and nothing noticed.
If a briefing names an Act or a set of Regulations that the source register does not cover, the build fails. It fails in the other direction too, so an entry nothing cites any more cannot sit there looking like diligence.
The date below is a constant, and a test fails once it is more than 182 days old. That is a deliberate time bomb. The law layer is the one part of this product that can become wrong while nobody touches it, so it is the one thing set to fail on a date rather than on a change.
Every phrase the eval treats as wrong is checked against the product's own legal context on every pull request. The first draft had five patterns that would have failed a correct answer, including one matching a sentence that is simply true. A broken instrument sends somebody hunting a bug that is not there.
Tests of the kind above check the code. They cannot check whether the answer the model actually writes is any good. So there is a second set of 17 fixed situations with known right and wrong answers, run against the live model and scored, which is what turns “the guidance is accurate” from a claim into a number.
The strongest check in it is negative. Each case lists phrases that would be actively wrong in UK employment law today, most of them the position before a recent change, which is exactly what a model reaches for when it is answering from memory. A phrase is either present or it is not, so there is nothing to argue about. Inventing a case name is a hard failure for the same reason: a citation nobody can check is the most damaging thing a model can produce, because a wrong case reads exactly like a right one.
Every run so far is below, including the ones that failed. Across the 20 runs, 234 of 255 cases have passed. Last updated 10th November 2026.
Run 1
5 passed, 3 failed
All three failures were faults in the eval rather than in the guidance. Two cases were written so loosely that a fair answer could not pass them, and one demanded a particular phrase rather than the point the phrase was standing for.
Run 20d7e703
7 passed, 1 failed
The eval again. Three cases asserted the same point with three separate lists of accepted wordings, one list had been widened and the other two had not, so a correct answer failed for a reason already fixed elsewhere in the same file. The lists are one shared constant now.
Run 39005925
5 passed, 3 failed
The first run that found a real defect, and it found two instances of it. The closing disclaimer came back wrapped in Markdown emphasis on the two most serious answers in the run, and nothing in the rendering path parses Markdown, so a reader would have seen the asterisks. Fixed in the prompt and repaired at render time. The third failure was the eval.
Run 4ba60106
8 passed, 0 failed
Every case passed.
Run 58d09b52
7 passed, 1 failed
The eval again. The first run after names were taken out of everything sent to the model, and the one failure was a correct answer: it said protection depends on the worker reasonably believing the information shows wrongdoing and that the concern does not have to prove correct, which is the test the case looks for. The accepted wordings had "reasonably believe" but not "believing", and now accept every form of the word.
Run 6a1a00c1
8 passed, 0 failed
Every case passed.
Run 76c8b345
8 passed, 0 failed
Every case passed.
Run 80b17dc0
7 passed, 1 failed
A real weakness, if a small one. Run after a live test on 12th October found nine situations giving the old tribunal time limit, which the eval had not been pointed at. The probation answer named discrimination only in its closing disclaimer and never said that those claims, and automatically unfair dismissals, need no qualifying service, which is the point of that case. The system prompt now states it for every situation.
Run 988890e3
14 passed, 1 failed
The first run across all fifteen situations, and the one failure was the eval. The probation answer made the point the case looks for, that discrimination and automatically unfair dismissal claims "do not require any minimum service", in a wording the shared list did not yet accept. It does now.
Run 105edc4b9
14 passed, 1 failed
The first scheduled weekly run, and again the one failure was the eval. The TUPE answer said a change made because of the transfer is "generally ineffective", which is the rule the case looks for, but the case only accepted the word void and two other phrasings. It now accepts this one too.
Run 11d3a1824
13 passed, 2 failed
The eval again, twice. Both failures were correct answers saying the qualifying period "remains two years" for a dismissal before 1st January 2027, which is true, and one pattern for the claim that two years survives 2027 matched the phrase without looking at the date it was tied to. It now skips a sentence tied to a date before 1st January 2027, and both answers are kept as tests.
Run 12c4542e8
15 passed, 0 failed
Every case passed. Started by hand after nine dependencies were updated, the OpenAI library among them, to check the guidance still came through.
Run 1310624b5
15 passed, 0 failed
Every case passed. Run on the law review of 30th October before it was merged, with the harassment duties moved to the past tense and the 2027 dates moved to the government timeline of 22nd October.
Run 14bb04818
14 passed, 2 failed
The first run of sixteen cases. The new one, a grievance about a customer's sexual comments, passed: the answer gave the duty to take all reasonable steps and the employer's liability for the customer, which the live site had left out that morning. No answer used the old reasonable steps standard. Both failures were the eval. The whistleblowing answer said dismissal is automatically unfair without any qualifying period, and the TUPE answer said agreement would not normally make the change valid where the transfer is the reason. Those are the points the two cases look for, in words they did not accept, and both wordings are now accepted.
Run 15471077a
16 passed, 0 failed
Every case passed. The scheduled weekly run of 2nd November.
Run 16340ca21
14 passed, 2 failed
Started by hand on the change that states the Scottish order made on 3rd November, which moves contract claims in Scotland to six months where employment ends on or after 9th November 2026. Both failures were the eval, and one came from that change. The non-compete answer said, correctly, that a Scottish contract claim where employment ends before that date keeps three months minus one day, and the time limit pattern did not know the Scottish exception. The whistleblowing answer said the ordinary qualifying period will reduce to six months, but whistleblowing protection applies from day one, and the pattern did not notice the but. Both now leave those sentences alone and still catch the wrong claims.
Run 17d44e9aa
15 passed, 2 failed
Started by hand on the change that names wrongful dismissal in the formal disciplinary briefing, after that morning's live run gave a Glasgow summary dismissal no mention of it. The seventeenth case, the same facts, passed. Both failures were the eval. The disciplinary answer gave the Scottish contract claims limit correctly, six months where employment ended on or after 9th November 2026 but three months minus one day where it ended earlier, and the time limit pattern only recognised an earlier date written as before. The TUPE answer called the pay and holiday cuts prohibited transfer related variations, which is what void means there, in words the case did not accept. Both wordings are now accepted.
Run 18bdfcbd8
16 passed, 1 failed
Started by hand on the change that says when a possible risk makes a situation high, after the first consistency check gave an informal lateness case medium, high and high on the same facts. Every case whose minimum is high came back high, and the consistency check on the same commit gave the lateness case medium all three times. The one failure was the eval: the TUPE answer said harmonising contracts is not a lawful reason for changing transferred terms, which is the point the case looks for, in words it did not accept. That wording is now accepted.
Run 1975bfb5a
17 passed, 0 failed
Every case passed. Started by hand on the change that measured what Tarn's letters cost to write. The same run wrote ten letters and two handbook sections with six model settings, and that is how letters came to be written without the model's reasoning: every one still met its legal points.
Run 20a1024f7
16 passed, 1 failed
Started by hand on the change that writes letters without reasoning and adds a letters eval, whose ten letters and two handbook sections all passed. The one failure was the eval. The Scottish disciplinary answer said that where employment ended before that date the limit would remain three months minus one day, which is right, with the words ahead of the figure in a form the time limit pattern did not accept. It now does.
Most of those failures turned out to be faults in the eval rather than in the guidance, which is worth saying plainly because it cuts both ways. The guidance held up under every case that was fairly put. The instrument has so far been less reliable than the thing it measures, which is normal for a new instrument and is not a reason to trust it less.
The eval catches drift, a model that starts writing differently and the specific confident wrongness the legal briefings exist to prevent. It does not check whether the law was applied correctly to your facts. Nothing automated can. That still needs a person, and on a serious matter that person should be a solicitor.
Tarn.hr is guidance, not legal advice, and it says so in every answer it writes. It tells you when a situation has gone beyond what it can help with rather than pressing on. The disclaimer sets out the limits in full.
There is no accuracy percentage on this page, and there will not be one. A set of 17 cases is too small to carry a figure like that honestly, and any number produced from it would say more about the cases than about the product. What the set is for is catching the thing that has gone wrong, which it has done twice.
If you find guidance on Tarn.hr that is wrong, please tell us. It is read by the person who can fix it, and a case that catches it goes into the set above so it cannot come back.