When must I present a whistleblowing detriment ET1?

Present this whistleblowing detriment ET1 within six calendar months less one day when the established operative event is on or after October 1, 2026. Earlier events retain three months less one day. Applicable ACAS dates can extend the limit.

Responsible actor. The worker presenting a protected-disclosure detriment complaint.

Use the detriment date, the last of an established series of similar acts or failures, or the statutory decision date for a deliberate failure. The disclosure date alone does not start this clock.

SI 2026/954 regulation 4 retains the old limit for an earlier relevant act or failure. For an established series, its last act or failure selects the transition.

Use the detriment date, the last of an established series of similar acts or failures, or the statutory decision date for a deliberate failure. The disclosure date alone does not start this clock. This calculator supports established operative events in 2026 and 2027. It does not decide disputed events, eligibility, continuing conduct, a qualifying series, extension applications or case-specific directions.

1. Use the detriment date, the last of an established series of similar acts or failures, or the statutory decision date for a deliberate failure. The disclosure date alone does not start this clock.
2. Select three months before October 1, 2026 or six months on or after that date.
3. Include the operative day in the statutory calendar-month period. End before the corresponding date in the target month, or on its last day when that corresponding date does not exist.
4. Apply supported ACAS dates separately, without reviving an already expired limit.
5. Statutory claim limitation includes weekends and bank holidays. Rule 5(2) does not provide a next-working-day carry for this statutory period.

Include the operative day in the statutory calendar-month period. End before the corresponding date in the target month, or on its last day when that corresponding date does not exist.

Statutory claim limitation includes weekends and bank holidays. Rule 5(2) does not provide a next-working-day carry for this statutory period.

Fictitious example

The established date of the established detriment or deliberate failure is October 8, 2026. No ACAS adjustment applies.

Fictitious established facts. These examples do not establish eligibility, the operative event, continuing conduct, a qualifying series, granted relief, valid ACAS receipt or completed presentation.

Does making the disclosure start this deadline?

The section 48(3) clock follows the complained-of detriment or failure, rather than the protected disclosure itself. Establish the detriment and its date.

Can later acts form a series?

Section 48(3)(a) uses the last act or failure in a series of similar acts or failures. Whether that series exists requires a separate assessment.

How do I date a deliberate failure to act?

Section 48(4) uses the decision date. An inconsistent act or expiry of the reasonably expected period can supply the date when no contrary evidence exists.

October 1, 2026 transition

SI 2026/954 regulation 4 retains the old limit for an earlier relevant act or failure. For an established series, its last act or failure selects the transition.

One timely ACAS notification

One timely ACAS notification for the same matter can be calculated. Pre-event notification, repeated certificates and disputed actual or deemed receipt need separate review. Day A must be on or after the operative event and no later than the original deadline. Day B is actual receipt or earlier deemed receipt.

• Use the detriment date, the last of an established series of similar acts or failures, or the statutory decision date for a deliberate failure. The disclosure date alone does not start this clock. This calculator supports established operative events in 2026 and 2027. It does not decide disputed events, eligibility, continuing conduct, a qualifying series, extension applications or case-specific directions.
• One timely ACAS notification for the same matter can be calculated. Pre-event notification, repeated certificates and disputed actual or deemed receipt need separate review.

• Use the detriment date, the last of an established series of similar acts or failures, or the statutory decision date for a deliberate failure. The disclosure date alone does not start this clock.
• Verify the governing provision and any actual Tribunal direction.
• Use the prescribed form and complete required minimum information.
• Check the applicable ACAS certificate or exemption where required.
• Preserve the form, operative-event evidence and Tribunal submission receipt.
• Present the prescribed claim and any required application by the end of the statutory final day, before midnight. Preserve the submission receipt. A draft or ACAS contact does not complete presentation.