Acas Early Conciliation: The ET1 Trap Claimants Cannot Afford to Miss

Why this article follows the Employment Tribunal time-limit article

Legal Lens recently looked at Employment Tribunal time limits in 2026 and the risk of assuming that every claimant now has six months. This article deals with the next procedural step: Acas Early Conciliation.

For most Employment Tribunal claims, the claimant must notify Acas before presenting the ET1. Acas describes Early Conciliation as a legal process for people considering an Employment Tribunal claim. When the claimant notifies Acas, Acas offers Early Conciliation. Taking part in settlement discussions is voluntary: the claimant and employer can choose whether to engage.

What Acas Early Conciliation is

Early Conciliation is the pre-claim process in which Acas speaks to the claimant and the respondent about the dispute, to see whether it can be resolved without an Employment Tribunal claim.

If Early Conciliation does not resolve the dispute, Acas gives the claimant a certificate with a number. Acas says this is the number needed for form ET1 if the claimant decides to make an Employment Tribunal claim.

Acas is impartial. It can explain its role, discuss the issues, give an overview of the relevant law and explore settlement. But Acas says it cannot represent either side, say whether to settle, assess the strength of the case, help prepare the tribunal case, or predict the outcome.

Early Conciliation is not a substitute for limitation advice

Acas’s current guidance says that most Employment Tribunal claims have a time limit of three months minus one day, while a few claims have six months minus one day. Acas also says the claimant should usually notify Acas within the applicable Employment Tribunal time limit.

Acas gives examples of when time starts. For unfair dismissal, it normally starts from the effective date of termination. For pay and wages, it starts from the date the worker was not paid correctly. For discrimination, it starts from the date of the last act of discrimination included in the claim. Acas also warns that time limits can be complex where there are multiple claims, multiple incidents, or continuing problems.

The key point is this: Early Conciliation can affect the deadline, but it does not remove the need to calculate the deadline.

Acas says time is paused when the claimant notifies Acas, but only if Acas is notified within the Employment Tribunal time limit. GOV.UK T420 guidance says submitting the Early Conciliation form “stops the clock”, and that time starts running again when the claimant is deemed to have received the Acas certificate.

Acas says that if the claimant notified Acas within time, they will have at least one month from the date they received the certificate to make the tribunal claim. Acas also warns that working out the exact time limit can be complicated, that the claimant remains responsible for filing in time, and that only a Tribunal can decide whether the claim is in time.

Do not wait for a grievance, appeal or settlement discussion

A common mistake is to wait for an internal process to finish before notifying Acas. That can be dangerous.

Acas says raising the problem with the employer first does not change the time limits for making an Employment Tribunal claim.

The same caution applies to settlement discussions, document requests, subject access requests and informal correspondence. They may matter evidentially or strategically, but they do not automatically stop the tribunal limitation clock.

The Acas certificate number matters

If Early Conciliation does not resolve the dispute, Acas gives a certificate with a number. Acas says that number must be put on the ET1.

GOV.UK’s T420 guidance says the ET1 must include the Early Conciliation certificate number or numbers provided by Acas, or a declaration that the claimant is exempt from the requirement to go through Early Conciliation. It also says the claim cannot be accepted unless certain conditions are met, including providing the certificate number or numbers, or an exemption declaration.

The certificate is not a formality to paste into the ET1 at the last minute. It is part of the Tribunal’s gatekeeping process.

What the Employment Tribunal Procedure Rules 2024 say

The Employment Tribunal Procedure Rules 2024 are the key procedural source. Rule 12 says the Tribunal must reject a claim if it is not made on a claim form, does not contain each claimant’s name and address and each respondent’s name and address, or does not contain one of the following: an Early Conciliation number, confirmation that the claim does not institute relevant proceedings, or confirmation that an Early Conciliation exemption applies.

Rule 13 deals with substantive defects. Tribunal staff must refer certain claims to the Tribunal, including where the claim appears to lack required Early Conciliation information, wrongly claims an exemption, contains an Early Conciliation number that does not match the certificate, or contains a claimant or respondent name that does not match the relevant Acas certificate.

That is a limited safety valve. It is not a reason to be casual.

Wrong exemption claims are high risk

Some claims are exempt from Early Conciliation. GOV.UK’s T420 guidance lists examples, including where another claimant on the same form has complied with Early Conciliation, where Acas has no power to conciliate, where the previous employer has already contacted Acas, or where the claimant is making an interim relief claim. GOV.UK also warns that incorrectly claiming an exemption may lead to rejection.

The Employment Tribunal Procedure Rules 2024 go further procedurally. Where relevant proceedings are brought on a claim form that says an Early Conciliation exemption applies, but no exemption applies, the Tribunal must reject the claim or the relevant part of it.

Interim relief: the urgent exception

Interim relief needs separate treatment. It is urgent and unusual.

Acas says an interim relief application must be made within seven days of the effective date of termination. In most cases, that means the last day of the notice period, or the date of dismissal if there was no notice.

Acas also says interim relief is available only in specific automatically unfair dismissal situations, including dismissal because the employee made a protected disclosure, carried out certain representative duties, took part in trade union activities, or fell within other listed categories.

The Early Conciliation position is different depending on the claim. Acas says that if an employee applies for interim relief alongside an unfair dismissal claim only, they do not need to notify Acas and only need to complete form ET1. But if the employee is making other claims at the same time, such as discrimination, they must also notify Acas.

Multiple respondents: check each respondent carefully

Multiple respondents create another trap.

GOV.UK’s T420 guidance says that if a claimant proposes to bring a claim against more than one prospective respondent, they must complete a separate form for each respondent. It also says that where more than one prospective respondent is named, Acas will issue an individual certificate with a unique reference number for each prospective respondent.

The same guidance says separate Acas certificate numbers must be provided for each respondent named in the ET1.

The vLex/legal research supports caution here. It records first-instance support for separate Early Conciliation compliance against each respondent, but says no supplied appellate authority squarely resolves every multiple-respondent scenario.

Respondent-name mismatches: minor errors may not be enough, but do not rely on that

The respondent name on the ET1 should match the respondent name on the Acas certificate. GOV.UK’s T420 guidance expressly warns that if the respondent’s name does not match the Acas certificate, the claim may be rejected.

The Employment Tribunal Procedure Rules 2024 allow a limited interests-of-justice exception for some name or address errors. The vLex/legal research says minor or same-entity discrepancies may sometimes be treated leniently, but that the position is fact-sensitive and should not be overstated.

The practical lesson is to use the correct legal name where possible, check the contract, payslip or Companies House if dealing with a company, and avoid relying on informal trading names where the legal identity matters.

Presenting the ET1 before the certificate exists

One of the most serious errors is presenting the ET1 before an Acas certificate exists, where Early Conciliation is required and no exemption applies.

The vLex/legal research says the authorities supplied support a strict gateway approach, particularly where a claim was presented before any certificate existed. It notes that later provision of the number will often not cure the original defect, and that in some cases the proper step may be fresh presentation after the certificate has been obtained.

That should be expressed carefully. Not every procedural defect has the same consequence, and the current Rules contain some limited safety valves. But claimants should not plan around those safety valves.

Can a mistake be corrected later?

Sometimes there may be a route to challenge or correct rejection.

The Employment Tribunal Procedure Rules 2024 say that a claimant whose claim has been rejected under rule 12 or rule 13 may apply for reconsideration on the basis that the rejection decision was wrong, or that the notified defect can be rectified. The application must be in writing and received within 14 days of the date the rejection notice was sent.

A reconsideration route is not the same as an automatic cure.

The Rules also say that if the Tribunal decides the original rejection was correct but the defect has been rectified, the claim is treated as presented on the date the rectification application was received.

Do not put Early Conciliation discussions in the ET1

GOV.UK’s T420 guidance says details of Early Conciliation discussions should not be included in the claim form.

That makes sense. The ET1 should set out the claim: the legal complaint, the facts relied on, the dates, the respondents, and the remedy sought. It is not the place to narrate protected settlement discussions or repeat what was said during conciliation.

A claimant can say that the Acas process has been completed and include the certificate number. The claim itself should focus on the pleaded issues.

Employer requests do not stop the clock

Employers can also contact Acas to request talks if they think a dispute with a worker could lead to a tribunal claim. But Acas says the tribunal time limit is not put on hold if the employer is the one who notifies Acas.

For employers, that matters because requesting Early Conciliation is not the same as controlling the claimant’s limitation period. For claimants, it matters because an employer’s contact with Acas should not be treated as a substitute for checking your own position.

Later-arising events and new claims

Some disputes develop after the Acas notification. New events may happen. A dismissal may follow earlier detriments. A grievance may produce new facts. A discrimination complaint may involve later acts.

Our research says the supplied materials do not provide a direct appellate authority fully resolving how far later-arising claims or events can be included after Acas notification. It recommends caution and says this issue may depend on whether the matters are part of the same dispute, whether an exemption applies, and whether the Tribunal is being asked to accept an amendment rather than a fresh claim.

Practical checklist before submitting the ET1

Conclusion

Acas Early Conciliation is important, but it is not a safety net.

It can pause time. It can produce the certificate needed for the ET1. It can help resolve disputes without litigation. But it does not calculate the deadline for the claimant, it does not provide legal advice, and it does not cure every defect in the ET1.