Guides › Energy and Water Bills › What Is a Deadlock Letter?
What Is a Deadlock Letter?
A deadlock letter is a business’s final response to your complaint, saying it will not do any more. It matters because it usually lets you go straight to the free ombudsman or ADR scheme, instead of waiting the full time the business is allowed (often 8 weeks; 6 weeks for phone and broadband; 40 working days for trains).
At a Glance
Your Rights
What the rules say, with a link to the official source for each.
Energy
The Energy Ombudsman
If your energy complaint is not resolved within 8 weeks, or you get a deadlock letter, you can take it to the Energy Ombudsman. It is free and impartial. source
Phone and Broadband
Free Dispute Resolution
If your complaint is not resolved, you can use a free alternative dispute resolution (ADR) scheme once six weeks have passed since your initial complaint, or earlier if you receive a deadlock letter. The two schemes are the Communications and Internet Services Adjudication Scheme (CISAS) and the Communications Ombudsman. All providers must belong to one. source
Trains
The Rail Ombudsman
If you are unhappy with how the train company handled your complaint, the Rail Ombudsman is free and independent. Allow the company 40 working days to resolve your complaint, or until it sends a final response (a deadlock letter) if that comes sooner. source
Time Limits to Know
Miss a deadline and you can lose a right. Check the dates on your own paperwork.
- 8 weeksEnergy complaint to the Energy OmbudsmanAfter 8 weeks with no resolution, or on receiving a deadlock letter
- 6 weeksWait before going to a free ADR schemeSix weeks from your complaint, or earlier with a deadlock letter
- 40 working daysWait before going to the Rail Ombudsman40 working days from your complaint, or until the company sends a final response (deadlock letter)
Steps to Take
Step 1 of 5
Complain to the business in writing and keep a copy.
Step 2 of 5
If you are not getting anywhere, ask in writing for its final response (a deadlock letter). Our free letter templates can write it for you.
Step 3 of 5
Keep the deadlock letter. It shows the business has finished dealing with your complaint.
Step 4 of 5
Take your complaint to the ombudsman or ADR scheme named in the letter, with your evidence.
Step 5 of 5
If no letter comes, you can usually go to the scheme once the waiting time has passed.
(Tap the numbers to reveal steps)
Where to Go If It Is Not Put Right
Your options, in order, and when each one applies.
Energy Ombudsman
After 8 weeks with no resolution, or when you get a deadlock letter.
CISAS or the Communications Ombudsman (ADR)
Six weeks after your complaint, or when you receive a deadlock letter. Free for you. Your provider will say which scheme it belongs to.
Rail Ombudsman
After 40 working days, or once you have a final response (deadlock letter), if the train company is a member of the scheme.
Good to Know
Small things that make your complaint stronger.
For banks and other financial firms, ask for a final response in writing. You have 6 months from the date of that final response to go to the Financial Ombudsman Service.
Want Help?
If you would like one of our team to look at your problem, our initial case review is free. We cannot guarantee any outcome and we do not give legal advice.
Lead reviewer
Luke Marley
Founder and Lead Reviewer
Luke founded CPUK in 2026 after seeing how hard it is for ordinary people to get problems with companies put right. He oversees our guides and checks them against official sources.
Research by Katie Burt, Co-founder and Operations Lead (17 years in the care sector, including managing services for vulnerable adults), and the CPUK Research Team. Researched with AI-assisted research tools, then checked and corrected by our team.
Last checked: 12 October 2026. We are not paid by the companies we write about. Adverts never affect our guidance. Read our editorial policy.
Sources and official links
- energyombudsman.org/advice-for-consumers/what-is-back-billing Checked 12 October 2026
- ofcom.org.uk/complaints/complain-about-phones-or-internet-services/contracts Checked 12 October 2026
- railombudsman.org Checked 12 October 2026