Building Your Complaint Evidence

Complaint schemes do not hold trials. An investigator reads your file and the organisation's file and decides, on the balance of probabilities, what most likely happened. The organisation's file is professionally maintained — system notes, call logs, dated letters. If yours is a recollection, you lose the tie.

So gather evidence that does one of three things: proves what happened, proves what was promised, or proves what it cost you.

• Written communications: emails, letters, live chat transcripts, app messages. Export them; do not rely on an account you might lose access to.
• Contract and terms: the version in force when you signed, not the one on the website today.
• Invoices, bills, and bank statements: these turn "I was overcharged" into a figure.
• Photographs and video: dated where possible, with something in frame for scale. Essential for repairs, workmanship, and goods.
• Medical evidence: a GP letter or record where you claim health impact — an ombudsman will rarely accept distress at the higher end without it.
• Contemporaneous diary: a note made at the time carries far more weight than one written afterwards. Record the date, time, who you spoke to, the reference given, and what they said.

Article 15 of the UK GDPR, with the Data Protection Act 2018, gives you the right to a copy of the personal data an organisation holds about you. A Subject Access Request is free, can be made in any format including email, and must be answered within one calendar month — extendable by up to two further months where the request is complex, but only if the organisation tells you within the first month.

A SAR is the single most useful step in a contested complaint, because it produces the material the organisation was never going to send you:

• Call recordings and call transcripts.
• Internal case notes, adviser comments, and system audit trails showing who did what and when.
• The decision record — often revealing that a policy was applied wrongly, or that an exception was granted to others.
• Complaint handling records, including internal escalation notes.
• Medical records held by an NHS body.

Be specific: "all call recordings, correspondence, system notes and complaint records relating to account [number] between [date] and [date]". Vague requests invite vague answers. Organisations may redact third-party personal data and legally privileged material, but they cannot withhold your data simply because a complaint is running. If they miss the deadline or over-redact, that is a complaint to the Information Commissioner's Office.

The document that wins cases is a one-page numbered chronology: date, what happened, and the document number that proves it. Everything else hangs off that page.

• Chronology — one line per event, in date order, with a document reference.
• Numbered documents — name files "01 - contract 12-03-2026.pdf", "02 - final response 18-06-2026.pdf". Do not send an unsorted folder.
• A loss schedule — each item of loss, the amount, and the document that evidences it, totalled at the bottom.
• Photos and screenshots as a single PDF with captions, not twenty separate image files.

Then reference them in the complaint itself: "the engineer failed to attend on 19 March (Document 4)". An investigator working through a heavy caseload will follow an argument they can check in seconds; they may not reconstruct one they cannot.

Send the material that carries the case first. You do not have to submit everything at once, and you can supply more when asked — but anything that goes to the heart of the dispute should be in from the start.

Covert recordings. Recording a call you are party to is not unlawful in the UK for your own use, and ombudsmen will sometimes admit such a recording. But recording others covertly can breach data protection rules if you then circulate it, and a recording obtained by deception invites an argument about your conduct rather than theirs. Where possible, get the same content through a SAR instead — the organisation's own recording is unimpeachable.

Hearsay and character material. "Someone who works there told me" and "they have terrible reviews online" carry no weight. Stick to what you witnessed, what you were told directly, and what is documented.

Volume. A 200-page bundle with six relevant pages is worse than a 10-page bundle with six relevant pages. Irrelevant material dilutes the case and buries the point.

Altered documents. Never edit, crop misleadingly, or annotate a document in a way that changes what it shows. If a document is discovered to have been altered, the investigator will discount your evidence generally, and that is usually fatal.

Evidence you obtained unlawfully — for example another person's records — can expose you to a claim in its own right. Leave it out.

When you refer to an ombudsman, send the chronology, the final response letter, the loss schedule, and the numbered documents. The scheme will obtain the organisation's file itself; you do not have to guess what is in it, but a SAR made before you refer lets you see the same material the investigator will see.

Most schemes issue a provisional view before the final decision. That stage is your last real chance to put in evidence, and it is the one most people waste by arguing rather than proving. If the view goes against you, respond by identifying the specific finding you say is wrong and attaching the document that contradicts it. New evidence at that stage is often accepted; new assertion rarely changes anything.

If the final decision still goes against you, keep the whole file. Do not accept the decision if you may litigate — acceptance binds you. Your bundle transfers almost unchanged into a small claims filing, and the six-year limitation period for most contract and negligence claims means the papers stay relevant long after the complaint ends.