What should a UK complaint letter include?

A complaint letter should include your details, the recipient’s details, a clear summary of the problem, key dates, supporting evidence, the remedy you want, and a deadline for response.

Should I attach evidence to a Letter Before Action?

You do not always need to attach every document, but you should refer to the key evidence and include copies where helpful. Keep original documents safe.

How should I organise evidence for a complaint letter?

Keep evidence in date order, label each document clearly, and create a short timeline of events. This makes your complaint easier to understand and review.

How long should I give the other party to respond?

A common deadline is 14 days, but more complex disputes may require longer. Some pre-action protocols require specific timeframes, so check whether one applies.

Can screenshots or photos be used as evidence?

Yes. Photos and screenshots can be useful if they clearly show the issue, date, sender, recipient, webpage, product defect, damage, or relevant conversation.

Can this checklist help me create an AI-generated complaint letter?

Yes. A checklist helps you gather the facts needed for an AI-generated complaint letter, so the final document is more accurate, complete, and persuasive.

What if I do not have all the evidence?

Missing evidence does not always prevent you from sending a complaint letter, but you should explain what you know, identify any gaps, and avoid making unsupported claims.

What are common mistakes in complaint letters?

Common mistakes include vague allegations, missing dates, no proof of loss, emotional language, unrealistic demands, and failing to give a clear deadline for response.

Should I keep copies of my complaint letter and evidence?

Yes. Keep a full copy of the complaint letter, all attachments, proof of sending, and any replies. These may be important if the dispute later goes to court.

How does this evidence checklist relate to the complaint letter generator?

This checklist supports the evidence-gathering stage. Once your documents and facts are ready, you can use the main complaint letter generator to create the letter.

EN-GB>Disputes>Letter Before Action>UK Complaint Letter Evidence Checklist

UK Complaint Letter Evidence Checklist

Created: 8 Jun 2026

This checklist helps UK readers gather the key evidence needed to support a strong complaint letter. Use it alongside our AI Generated British Letter Before Action resources to prepare clear, relevant and well-documented claims.

Complaint type	Purpose of evidence	Evidence importance	Example documents	Collection stage
Contract, Receipts and invoices, Payment record
Unpaid invoice for goods or services	Proves the agreed price, work supplied, due date and unpaid amount.	Essential	Signed contract, purchase order, invoice, statement of account, payment reminders.	Before drafting
Receipts and invoices, Contract, Payment record
Business late payment claim	Supports principal debt, due date, interest calculation and fixed recovery sum.	Essential	Invoice, credit terms, payment ledger, interest calculation, demand letters.	Before sending
Receipts and invoices, Photographs, Correspondence
Faulty goods bought from a retailer	Shows purchase details, defect, complaint date and requested remedy.	Essential	Receipt, order confirmation, photos of defect, retailer emails, warranty card.	Before drafting
Receipts and invoices, Photographs, Expert report
Goods not of satisfactory quality	Links the defect to the statutory quality standard and purchase condition.	Essential	Receipt, product photos, inspection report, repair quote, packaging details.	Before sending
Terms and conditions, Correspondence, Photographs
Goods not as described	Compares the description, advert or specification with what was supplied.	Essential	Product listing, brochure, screenshots, label photos, order confirmation.	Before drafting
Receipts and invoices, Correspondence, Photographs
Short-term rejection of faulty goods	Shows purchase date, prompt rejection and basis for a refund request.	Essential	Receipt, defect photos, rejection email, return request, retailer reply.	Before sending
Correspondence, Photographs, Receipts and invoices
Repair or replacement request for faulty goods	Proves the defect and records requests for repair or replacement.	Essential	Repair request, retailer emails, photos, collection notes, service reports.	Before sending
Delivery records, Receipts and invoices, Correspondence
Missing or undelivered parcel	Shows the order, delivery promise, tracking history and non-receipt.	Essential	Order confirmation, tracking page, courier photo, retailer chat, delivery complaint.	Before drafting
Photographs, Delivery records, Receipts and invoices
Goods damaged in delivery	Shows condition on arrival, packaging damage and delivery timing.	Essential	Unboxing photos, damaged packaging photos, courier note, order receipt.	Before drafting
Contract, Delivery records, Correspondence
Late delivery after agreed date	Proves agreed delivery date, delay and any cancellation or loss.	Essential	Delivery promise, tracking history, seller emails, cancellation notice, loss receipts.	Before sending
Contract, Photographs, Expert report
Service not performed with reasonable care and skill	Shows agreed service, poor workmanship and cost to correct it.	Essential	Quote, scope of works, before and after photos, snagging list, repair estimate.	Before drafting
Contract, Correspondence, Photographs
Request for repeat performance of service	Shows defects in the service and previous opportunity to fix them.	Helpful	Job sheet, complaint emails, photos, rework request, contractor response.	Before sending
Contract, Receipts and invoices, Expert report
Price reduction for poor service	Supports the amount paid, reduced value and proposed refund.	Essential	Invoice, payment proof, defect list, valuation, remedial quote.	Before sending
Contract, Photographs, Expert report
Defective building or trade work	Proves scope, defects, causation and reasonable repair cost.	Essential	Written quote, plans, progress photos, snagging report, surveyor report, repair estimates.	Before court claim
Contract, Correspondence, Other
Building work delay	Shows agreed timetable, delay events and extra costs caused.	Helpful	Project schedule, messages, site diary, completion dates, accommodation receipts.	Any stage
Receipts and invoices, Expert report, Correspondence
Poor vehicle repair or garage service	Shows requested work, faults after repair and cost of rectification.	Essential	Garage invoice, MOT record, diagnostic report, mechanic report, photos, emails.	Before court claim
Terms and conditions, Photographs, Expert report
Used car not as described	Compares advert claims with vehicle condition, history and faults.	Essential	Dealer advert, HPI check, service history, inspection report, photos, invoice.	Before sending
Contract, Receipts and invoices, Correspondence
Faulty car bought on finance	Identifies dealer, lender, finance terms and complaint history.	Essential	Finance agreement, dealer invoice, complaint emails, repair reports, payment schedule.	Before sending
Payment record, Contract, Correspondence
Credit card Section 75 claim	Shows credit card payment, supplier breach and linked transaction.	Essential	Card statement, invoice, booking confirmation, supplier complaint, refund refusal.	Before drafting
Payment record, Correspondence, Delivery records
Debit or credit card chargeback request	Supports non-delivery, faulty goods, cancelled service or failed refund.	Helpful	Card statement, order confirmation, tracking, cancellation email, trader refusal.	Before sending
Receipts and invoices, Terms and conditions, Correspondence
Cancelled event refund	Shows booking, cancellation, refund entitlement and organiser response.	Essential	Tickets, booking confirmation, event cancellation notice, refund policy, emails.	Before drafting
Contract, Receipts and invoices, Photographs
Package holiday complaint	Shows promised package, failures, complaints made in resort and losses.	Essential	ATOL certificate, itinerary, hotel photos, complaint forms, receipts, emails.	Before sending
Receipts and invoices, Correspondence, Other
Flight cancellation or delay compensation	Shows flight details, delay length, airline reason and expenses.	Essential	Boarding pass, booking reference, delay notice, airline emails, meal receipts.	Before drafting
Contract, Photographs, Correspondence
Hotel or accommodation not as booked	Compares booking description with actual accommodation and complaints made.	Essential	Booking page, confirmation, room photos, reception complaint, alternative hotel receipts.	Before sending
Contract, Payment record, Correspondence
Tenancy deposit not protected or not returned	Shows deposit paid, tenancy terms, protection status and deductions disputed.	Essential	Tenancy agreement, bank transfer, deposit certificate, inventory, landlord emails.	Before drafting
Correspondence, Photographs, Expert report
Landlord failure to carry out repairs	Shows disrepair, notice to landlord, delay and effect on the tenant.	Essential	Repair emails, damp photos, council report, contractor quote, rent account.	Before sending
Photographs, Correspondence, Expert report
Rented home unfit for human habitation	Shows hazards, landlord notice and impact on use of the property.	Essential	Damp photos, hazard report, medical notes, repair requests, council letters.	Before court claim
Contract, Bank statements, Correspondence
Rent arrears demand	Shows rent due, payments made, arrears balance and notices sent.	Essential	Tenancy agreement, rent schedule, bank statements, arrears letters, payment plan.	Before drafting
Photographs, Expert report, Correspondence
Neighbour caused property damage	Shows damage, likely cause, repair cost and prior notice to neighbour.	Essential	Damage photos, surveyor report, repair quote, neighbour messages, insurance letters.	Before court claim
Other, Correspondence, Photographs
Private nuisance from noise, smoke or leaks	Shows frequency, severity, source and steps taken to resolve it.	Helpful	Noise diary, videos, council complaint, photos, neighbour letters, witness notes.	Any stage
Photographs, Expert report, Correspondence
Tree roots or branches causing damage	Shows damage, cause, ownership of tree and repair cost.	Essential	Arborist report, surveyor report, photos, land registry plan, repair estimates.	Before court claim
Contract, Correspondence, Expert report
Professional negligence claim	Shows retainer, advice given, breach, causation and financial loss.	Essential	Engagement letter, advice emails, file notes, loss calculation, independent expert view.	Before court claim
Contract, Correspondence, Receipts and invoices
Complaint about solicitor service	Shows retainer, service complaint, fees charged and firm response.	Essential	Client care letter, bills, emails, complaint letter, final response.	Before sending
Contract, Correspondence, Other
Accountant error or fee dispute	Shows agreed work, alleged error, tax impact and disputed fees.	Essential	Engagement letter, tax returns, HMRC letters, invoices, emails, penalty notices.	Before drafting
Contract, Terms and conditions, Correspondence
Estate agent fee or service dispute	Shows agency terms, commission trigger, marketing promises and complaint history.	Essential	Agency agreement, property listing, fee invoice, offer emails, complaint response.	Before drafting
Contract, Correspondence, Expert report
Insurance claim refusal or underpayment	Shows policy cover, claim facts, insurer reasons and value of loss.	Essential	Policy schedule, claim form, rejection letter, loss adjuster report, repair estimates.	Before sending
Bank statements, Correspondence, Other
Unauthorised bank transaction	Shows disputed transaction, reporting date and bank investigation response.	Essential	Bank statement, fraud report, bank messages, police reference, device logs.	Before drafting
Contract, Correspondence, Bank statements
Mis-sold financial product	Shows advice received, product features, suitability concerns and financial loss.	Essential	Application form, suitability report, policy documents, statements, complaint response.	Before sending
Receipts and invoices, Payment record, Correspondence
Energy, water or broadband billing dispute	Shows charges, readings, payments and supplier complaint handling.	Essential	Bills, meter readings, photos, direct debit records, complaint emails, final bill.	Before drafting
Contract, Correspondence, Other
Broadband or mobile service failure	Shows promised service, outages, speeds, complaint dates and compensation claim.	Helpful	Contract, speed tests, outage logs, provider texts, bills, complaint reference.	Any stage
Contract, Bank statements, Correspondence
Gym or subscription cancellation dispute	Shows cancellation rights, notice given and payments taken after cancellation.	Essential	Membership terms, cancellation email, direct debit records, app messages, refund request.	Before drafting
Terms and conditions, Bank statements, Correspondence
Online subscription auto-renewal dispute	Shows renewal terms, cancellation attempt and charges disputed.	Essential	Signup page, renewal email, terms, cancellation screenshots, bank statement.	Before drafting
Receipts and invoices, Correspondence, Other
Faulty digital content or software	Shows purchase, fault, compatibility issue and supplier response.	Essential	App receipt, licence terms, error screenshots, support tickets, system details.	Before sending
Receipts and invoices, Correspondence, Delivery records
Online marketplace seller dispute	Shows order, seller identity, platform messages and delivery or refund issue.	Essential	Marketplace order, seller profile, message thread, tracking, refund decision.	Before drafting
Contract, Correspondence, Payment record
Breach of business contract	Proves obligations, breach, notice, losses and attempts to resolve.	Essential	Signed agreement, variation emails, invoices, delivery notes, breach notice, loss schedule.	Before drafting
Contract, Correspondence, Receipts and invoices
Supplier failed to deliver business services	Shows deliverables, deadlines, fees paid and missing work.	Essential	Statement of work, project plan, milestone invoices, emails, incomplete deliverables.	Before sending
Receipts and invoices, Bank statements, Correspondence
Director or shareholder reimbursement dispute	Shows authorised expenses, company benefit and amount owed.	Essential	Expense receipts, board approval, bank statement, mileage log, reimbursement request.	Before drafting
Contract, Correspondence, Receipts and invoices
Freelancer or contractor non-payment	Shows agreed rate, completed work, invoice issued and payment chased.	Essential	Client brief, contract, timesheets, deliverables, invoice, approval emails.	Before drafting
Contract, Bank statements, Other
Unpaid wages or salary	Shows agreed pay, hours worked, deductions and shortfall.	Essential	Employment contract, payslips, rotas, timesheets, bank statements, wage query emails.	Before drafting
Contract, Payment record, Other
Unpaid holiday pay	Shows holiday entitlement, leave taken, pay received and shortfall.	Essential	Contract, holiday records, payslips, rota, payroll emails, leaver statement.	Before sending
Contract, Correspondence, Payment record
Unpaid notice pay	Shows notice entitlement, termination date and amount unpaid.	Essential	Employment contract, resignation or dismissal letter, payslips, final pay statement.	Before drafting
Correspondence, Other, Bank statements
Workplace discrimination complaint	Shows protected characteristic, treatment complained of, comparators and losses.	Essential	Emails, grievance, witness notes, rota changes, pay records, medical notes.	Before sending
Correspondence, Other
Data subject access request complaint	Shows request date, identity checks, deadline and missing response.	Essential	Subject access request, proof of sending, ID request, response, missing data list.	Before drafting
Correspondence, Other, Bank statements
Personal data breach or misuse	Shows breach, harm, financial loss and organisation response.	Essential	Breach notice, screenshots, fraud alerts, bank records, complaint emails, ICO correspondence.	Before sending
Other, Correspondence
Defamatory online statement	Shows the words used, publication, audience, serious harm and takedown request.	Essential	Screenshots with URL and date, analytics, customer messages, takedown emails.	Before drafting
Other, Correspondence, Receipts and invoices
Copyright or trade mark infringement	Shows ownership, copying, use in trade and loss or licence value.	Essential	Registration certificate, dated original files, screenshots, sales records, licence fees.	Before sending
Photographs, Correspondence, Payment record
Private parking charge dispute	Shows signage, payment, timing, keeper details and appeal history.	Helpful	Parking notice, machine receipt, sign photos, app payment, appeal decision.	Before sending
Photographs, Expert report, Receipts and invoices
Vehicle accident property damage claim	Shows liability, damage, repair cost, hire charges and insurer contact.	Essential	Accident photos, dashcam, repair estimate, hire invoice, police reference, insurer emails.	Before drafting
Expert report, Photographs, Other
Personal injury claim	Shows accident circumstances, injury, medical causation and financial losses.	Essential	Accident report, photos, medical records, wage loss evidence, receipts, witness details.	Before court claim
Receipts and invoices, Bank statements, Other
Small claim damages calculation	Shows how the claimed amount is calculated and evidenced.	Essential	Loss schedule, receipts, repair quotes, bank statements, replacement purchase records.	Before court claim
Correspondence, Other
Pre-action conduct and settlement attempts	Shows reasonable attempts to explain the dispute and avoid court.	Essential	Complaint letter, letter before action, replies, settlement offers, mediation proposals.	Before court claim
Delivery records, Correspondence, Other
Proof that complaint letter was sent	Shows the recipient received or was sent the complaint and deadline.	Essential	Recorded delivery receipt, email sent record, read receipt, certificate of posting.	Before sending
Contract, Receipts and invoices, Other
Identifying the correct defendant or trader	Confirms the legal name, address and entity responsible.	Essential	Invoice, company number, Companies House record, website terms, receipt, email footer.	Before drafting
Contract, Correspondence, Payment record
Checking claim limitation deadline	Identifies key dates for breach, payment, injury or knowledge.	Helpful	Contract date, invoice date, defect discovery date, last payment, acknowledgement emails.	Before court claim
Receipts and invoices, Correspondence, Other
Showing reasonable steps to reduce loss	Shows avoidable losses were limited and replacement costs were reasonable.	Helpful	Alternative quotes, temporary repair receipts, cancellation attempts, substitute supplier records.	Before court claim
Other, Correspondence
Witness support for disputed facts	Supports disputed conversations, events, condition of goods or accident facts.	Helpful	Witness names, signed notes, dated statements, messages confirming events.	Any stage
Complaint handled by phone	Records who was spoken to, when, and what was promised.	Helpful	Call logs, call reference numbers, follow-up emails, notes made immediately after calls.	Any stage
Other, Terms and conditions, Correspondence
Online evidence likely to change or disappear	Preserves adverts, terms, prices, reviews, messages or account pages.	Helpful	Screenshots with date, URL, full page capture, archived webpage, chat transcript.	Before drafting
Correspondence, Other
ADR or ombudsman escalation	Shows final response, deadlock, complaint timeline and escalation readiness.	Helpful	Final response letter, complaint reference, timeline, ADR scheme details, ombudsman form.	Before court claim

What Evidence Should You Collect Before Sending A Letter Before Action?

For most UK complaint letters, the strongest evidence is a clear paper trail showing what was agreed, what went wrong, what loss was caused, and what remedy you want. Collect the contract or order confirmation, proof of payment, key correspondence, dated photographs where relevant, and receipts or invoices for losses before drafting.

Why Are Contracts, Terms And Payment Records Usually Essential?

Contract terms, booking confirmations, invoices, receipts and bank statements help prove the basic elements of a civil claim: the parties, the price, the service or goods promised, and the loss suffered. In consumer disputes, these records also help connect the complaint to rights under the Consumer Rights Act 2015, including goods being of satisfactory quality, services being performed with reasonable care and skill, and digital content meeting statutory standards.

When Is Expert Evidence Worth Getting?

Expert reports are most useful for technical disputes, such as defective building work, vehicle repairs, damp, electrical work, professional negligence, or damage where the cause is disputed. They are usually not needed for a first complaint letter, but may become important before a court claim if the other party denies fault or the cost of repair is substantial.

What Should You Review Before Court Action?

Before issuing a UK civil claim, review all correspondence, delivery records, inspection reports, repair estimates, mitigation costs and settlement offers. The Practice Direction on Pre-Action Conduct and Protocols expects parties to exchange enough information to understand each other’s position and try to settle where possible, so your evidence should be organised and ready to attach or summarise.

How Should Evidence Be Presented In A Complaint Letter?

Use a short chronology and refer to each item of evidence by date and title, such as invoice dated 12 March or photographs taken on delivery. Keep originals safe and send copies only. Where goods, services or delivery issues are involved, include dates, reference numbers, tracking details, amounts paid, and the remedy requested, such as refund, repair, replacement, repeat performance, price reduction or compensation.

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FAQs

What is a UK Complaint Letter Evidence Checklist?

It is a practical list of the documents and details you should gather before drafting a UK complaint letter or Letter Before Action. It helps you present your claim clearly and support it with evidence.

What evidence should I include with a complaint letter?

What is a Letter Before Action in the UK?

What evidence is needed for a Letter Before Action?

Do I need evidence before sending a complaint letter?

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