Building Your Complaint Evidence

The type of evidence you need depends on the nature of your complaint, but the following are relevant to most situations:

• Written communications: Emails, letters, live chat transcripts, app messages. Save these in a dedicated folder and do not delete them.
• Contracts and terms: The original contract or terms and conditions you agreed to — essential if the complaint involves a breach of those terms.
• Invoices and statements: Bills, bank statements, and receipts that show what you were charged and when.
• Photographs and videos: Physical evidence of damage, poor workmanship, or substandard conditions — particularly useful for housing, repairs, or consumer goods complaints.
• Medical records and notes: If your complaint involves health impacts, a letter from your GP or consultant can corroborate your account.
• Complaint diary: A contemporaneous record of events as they happened, including dates of phone calls, names of representatives, and what was agreed.

Under the UK General Data Protection Regulation (UK GDPR) and the Data Protection Act 2018, you have the right to request all personal data an organisation holds about you. This is known as a Subject Access Request (SAR). There is no fee to make a SAR, and the organisation must respond within one calendar month.

SARs are particularly powerful tools for complaint evidence because they can reveal:

• Records of all phone calls (including call recordings in many cases)
• Internal notes and case handler comments about your account or complaint
• Decision-making records that may reveal errors or inconsistencies
• Medical records held by NHS organisations
• Complaint handling records

To make a SAR, write to the organisation's Data Protection Officer (DPO) or use their online SAR request form if one exists. Be specific about the data you want — for example, "all call recordings, written communications, and account notes relating to my account from [date] to [date]".

Well-organised evidence is easier for an ombudsman or decision-maker to follow. Consider creating a simple file structure:

• Timeline document: A chronological list of events, including dates of contacts, what was said, and any outcomes. This is your master reference.
• Correspondence folder: All emails and letters in date order.
• Documents folder: Contracts, statements, invoices, and other reference documents.
• Media folder: Screenshots, photos, and videos.

When submitting a complaint, you do not need to send everything at once. Start with the most relevant documents and be prepared to provide additional evidence if the ombudsman or investigator requests it.

Number your documents and reference them in your complaint letter ("see Document 3 — billing statement dated 15 January 2025"). This makes it much easier for the person reviewing your case to follow your argument.

Some forms of evidence can be counterproductive or inadmissible. Be aware of the following:

• Covert call recordings: Recording a phone call without telling the other party is not illegal under UK law if you are one of the parties, but covert recordings of third parties without consent can be problematic. Check the rules if you intend to use a recording made without consent.
• Hearsay evidence: Statements like "my friend who works there said..." are unlikely to carry weight. Stick to what you personally witnessed or documented.
• Irrelevant material: Including large volumes of marginally relevant documents can dilute your complaint. Focus on what directly supports your key points.
• Altered documents: Never alter or annotate documents in a way that misrepresents them. This could undermine your entire case.