Here's the thing: most students write complaint letters that sound like they're filing a police report, not actually talking to someone. You know the feeling. You spend 20 minutes crafting what feels like a solid letter, hand it in, and find out it scored a Band 5. Why? Because you missed half of what the examiner was actually looking for.
This guide fixes that. I'm going to walk you through exactly how examiners score your complaint letter, which mistakes kill your score fastest, and how to use an IELTS writing checker to push toward Band 7.
Let me be straight with you. Band 4 and Band 5 letters share one fatal flaw: they don't give examiners what they're actually looking for. You're graded on five specific criteria, and most students only nail two of them.
The five criteria are Task Response, Coherence and Cohesion, Lexical Resource, Grammatical Range and Accuracy, and letter format. Here's what kills you: a grammatically perfect letter that buries the complaint? That's Band 5 max. A letter that nails all the content but sounds too casual? Band 6 ceiling, probably lower.
The mistake most students make is thinking the complaint letter is just about saying you're unhappy. It's not. You need to hit specific structural and linguistic targets while staying formal the entire time, all within 150–220 words and 20 minutes flat.
Task Response asks: Did you actually answer the prompt? For complaint letters, this means you need to:
Band 7+ students get this: "I'm not happy" isn't Task Response. That's just a feeling. Here's what I mean:
Weak (Band 4–5): "I ordered a laptop from your website three weeks ago and it hasn't come yet. This is really frustrating because I need it for work. Please send it to me as soon as possible."
Strong (Band 6–7): "I purchased a laptop (Order #45829) on August 15th, which was promised for delivery by August 28th. However, three weeks have now passed without arrival. This delay has prevented me from meeting project deadlines at work. I would appreciate either a confirmed delivery date within 7 days or a full refund."
The strong version includes order numbers, specific dates, what went wrong, and what needs to happen next. The weak version leaves the reader guessing.
Tip: Ask yourself: Could the reader act on this without emailing me back with questions? If the answer is no, you haven't nailed Task Response yet.
This criterion measures whether your letter flows logically and uses linking language to connect ideas. A Band 6 letter is organized. A Band 7 letter is organized and uses sophisticated transitions to show how ideas connect.
Complaint letters follow a predictable structure, and examiners expect it:
Most Band 5 students nail structure but fail on linking. Here's the difference:
Weak (Band 5): "Dear Sir or Madam, I am writing about the faulty hairdryer I bought from your shop. It stopped working after two days. I want a refund. I hope you can help."
Strong (Band 6–7): "Dear Sir or Madam, I am writing to lodge a formal complaint regarding a faulty hairdryer (Model X200, purchased 5 September) from your store on Fifth Avenue. Although the product worked initially, it ceased functioning after only two days of use. Consequently, I was unable to prepare for a client presentation and incurred additional costs for an emergency replacement. I would therefore appreciate either a full refund or an exchange for a functioning unit within 10 business days."
The strong version uses transitions like "Although," "Consequently," and "Therefore" that connect ideas. The weak version just lists problems. That's a 1–2 band point swing right there.
Tip: Use linking phrases like "However," "As a result," "In addition," and "Therefore" to show how your sentences connect. An IELTS task 1 letter evaluation should flag missing transitions.
Lexical Resource is about using varied, accurate vocabulary in the right register. Band 5 students use basic words. Band 7 students use precise, formal vocabulary that fits the context.
Look at this side-by-side:
Weak (Band 5): "The food was bad. It made me sick. I want my money back."
Strong (Band 7): "The meal was substandard and contaminated. I experienced severe gastrointestinal distress, requiring medical attention. I request an immediate refund and compensation for medical expenses."
Notice how "substandard" and "contaminated" replace "bad"? How "gastrointestinal distress" replaces "sick"? This is formal register, and it matters.
Here are vocabulary swaps you should memorize for complaint letters:
A good complaint letter checker will flag informal language and suggest formal alternatives. That single move can bump you from Band 6 to Band 7 on Lexical Resource alone.
Grammar mistakes hurt. One error might cost you 0.5 bands. Ten errors? You're capped at Band 5 no matter what else you do.
Most Band 5 letters suffer from the same problem: they're written entirely in simple sentences. "I bought a phone. It doesn't work. I want a refund." That's technically correct, but it's Band 4 grammar because you're not showing range.
Band 6 and 7 letters mix simple and complex sentences. They use subordinate clauses, conditionals, and passive voice.
Weak (Band 5): "I stayed at your hotel. The air conditioning did not work. I could not sleep. I want compensation."
Strong (Band 7): "During my three-night stay at your establishment, the air conditioning system in Room 412 failed to operate, which prevented me from sleeping adequately and resulted in considerable discomfort. If this matter is not resolved satisfactorily within 14 days, I will be forced to report the issue to local authorities."
The strong version uses passive voice ("the air conditioning system failed"), relative clauses ("which prevented me"), and conditionals ("If this matter"). These show range without being wrong.
Grammar mistakes that tank complaint letters:
A solid IELTS writing checker will catch these instantly. You should still proofread, but sometimes these small errors take 90 seconds to spot on your own.
Tip: Read your letter out loud before submitting. Grammar mistakes and awkward phrasing jump out when you hear them. This takes 30 seconds and catches errors you'd miss reading silently.
Format mistakes won't fail you outright, but they'll cap you at Band 6. You won't see examiners dock points for format alone, but they'll see an unprofessional letter and mark you down everywhere.
IELTS expects this structure:
[Your address] / [Date] / Dear Sir or Madam / [Body paragraphs] / Yours faithfully / [Your name]
Format mistakes examiners see constantly:
A formal complaint letter band score evaluation should flag these format issues. They're objective and easy to fix. When you're looking at proper letter salutations, make sure you're matching the formal tone throughout.
A good checker does three things: it identifies errors, explains why they're wrong, and suggests fixes. Not all checkers do all three.
Here's the strategic workflow:
Step 1: Write your draft without the checker. You've got 20 minutes to write under exam conditions. Don't stop to question every sentence. Write, finish, then check.
Step 2: Use the checker to identify Task Response gaps. Does your letter state the problem, explain the impact, and request resolution? If the checker flags that you're missing something, rewrite that section now.
Step 3: Review grammar and vocabulary flags. The checker will highlight non-standard structures and basic vocabulary. For each flag, decide: Is this a mistake I need to fix, or is it acceptable in this context?
Step 4: Check format manually. Your checker might miss letter conventions. Verify you've included a date, correct salutation, and proper closing.
Step 5: Read the final version out loud. This catches errors checkers miss and helps you spot anything that sounds non-native or awkward.
Tip: Don't rely solely on a checker to boost your band score. Checkers are tools, not tutors. They'll identify a grammar mistake, but understanding why it's wrong and how to avoid it next time matters more for improvement.
Let's take a real scenario. You've been given a prompt to complain about poor service at a restaurant.
Band 5 Version (Original):
"Dear Sir, I am writing about the bad service I got at your restaurant last week. When I came in, the waiter was rude. He did not bring my food for 45 minutes. Then the food was cold. I did not like it. I want a refund for my meal. Please reply soon. Yours faithfully, John."
This hits some basics but fails on multiple fronts:
Band 7 Version (Revised):
"[Your address], 8 September 2026. Dear Sir or Madam, I am writing to formally lodge a complaint regarding my dining experience at your establishment on 1 September. Upon arrival at 19:00, I was seated promptly; however, the service thereafter deteriorated significantly. The waiter displayed discourteous behavior and failed to deliver my order for nearly an hour, despite the restaurant being only moderately occupied. When my meal finally arrived, the food was cold and inedible. Consequently, I was unable to enjoy my evening and feel the establishment failed to meet basic service standards. I request either a full refund of £35 or a voucher for a complimentary meal at a future date. I look forward to your prompt response. Yours faithfully, John Smith."
This version demonstrates:
The difference isn't just length. It's structured differently, uses formal language consistently, and gives the reader everything they need to act.
Most students plateau at Band 6 on complaint letters. Here's why.
Band 6 letters are correct. They hit all the criteria. But they're safe. They use common vocabulary. They follow the formula without standing out.
Band 7 letters do something different. They demonstrate control over language. They choose strong verbs instead of weak ones. They vary sentence structure intentionally. They show sophistication without being pretentious.
Example: Band 6 student writes, "I was very unhappy with the service." Band 7 student writes, "I was thoroughly dissatisfied with the service, particularly given the premium price point."
The second version adds specificity ("given the premium price point") that shows critical thinking. It's not just complaint; it's reasoned complaint.
Not all writing correction tools are created equal. When choosing an IELTS writing evaluator for your complaint letter, look for these features:
The best tools give you feedback that helps you improve, not just corrections. An IELTS writing correction service should show you patterns in your mistakes so you don't repeat them.
Before hitting submit on your IELTS, run through this checklist:
If you can check all eight boxes, you're likely looking at Band 6 minimum. For Band 7, you also need sophisticated vocabulary choices and seamless transitions throughout.
Use our free IELTS writing checker to evaluate your letter against real band descriptors. Get instant feedback on Task Response, coherence, vocabulary, grammar, and format so you know exactly where you stand and how to reach Band 7.
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