Here's the real difference between a Band 6 and a Band 7 letter in IELTS General Training: it's not about length. It's not about fancy vocabulary. It's about argument strength. And most students have no idea how to evaluate their own.
You finish writing a formal complaint letter or a request for information. You read it back. It sounds fine. But you're not sure if it's strong enough to push you from 6.5 to 7. That nagging doubt? That's exactly what we're fixing today.
The band descriptors don't use the words "argument strength" directly. But they absolutely measure it. Look at Task Response and Coherence and Cohesion. A Band 7 response should "cover all parts of the task" and "present information clearly," while a Band 6 response might cover the task but with less precision or clarity.
In a letter, this comes down to one thing: does your reader understand exactly what you want and why you want it? A Band 6 letter gets the message across. A Band 7 letter makes it impossible to misunderstand.
That difference lives in argument strength. It's what holds your entire letter together. When you use an IELTS writing checker to evaluate your work, the first thing it assesses is how well you've supported each claim you make.
It's not about being aggressive or persuasive in a sales pitch way. It's about logical clarity and relevance.
When you write a letter, you're making claims. The manager ignored your complaint about the heating. The university rejected your application. You want a refund. Argument strength is how directly and clearly you connect your claim to your request.
A weak letter says "The service was bad." A strong letter says "The service was bad because X happened, which caused Y consequence for me, which is why I need Z solution."
Weak: I am not satisfied with the course. The teacher was not good. I want a refund.
Strong: I enrolled in the Advanced English course starting 1 September, but I have had to withdraw after only two weeks because the instructor's teaching method does not align with the course description. The syllabus promised grammar and speaking practice in equal measure, yet lessons have focused almost entirely on reading comprehension. As a result, I have not received the training I paid for, and I am requesting a full refund of the course fees.
See it? The strong version includes specifics: dates, what was promised, what actually happened, the consequence, and the request. That's argument strength at work.
Band 6 writers say things are "bad" or "wrong". Band 7 writers say what specifically is bad and how they know it.
Weak: The accommodation was not clean.
Strong: Upon arrival on 15 November, I found the kitchen countertops covered in crumbs and grease, and the bathroom had not been cleaned since the previous tenant's departure. This violated the "cleaned and inspected before arrival" guarantee in your rental agreement.
Notice what changed: the strong version has dates, specific locations, observable facts, and a reference to what was promised. Your reader can't argue with that. They can definitely argue with "not clean."
Link your evidence directly to why you're writing. Don't make your reader guess the connection.
Weak: The delivery arrived late. I was upset. Please send a discount code.
Strong: The delivery arrived on 10 December, three days after the guaranteed date of 7 December. Because I needed the items for a gift, the late arrival rendered the purchase unusable for its intended purpose. Given this failure to meet your stated delivery guarantee, I would appreciate a 20% discount on my next order as compensation.
The strong version shows what went wrong, when it went wrong, why it mattered specifically to you, and what you're asking for in response. That's cause and effect linking your problem to your solution.
Your request needs to match the severity of the problem. This isn't just logic. It's what makes your letter credible.
Weak: The waiter forgot my coffee. I demand a full refund of my entire meal and free meals for life.
Strong: The waiter forgot my coffee during my lunch appointment, which caused me to sit without a beverage for 15 minutes while my meeting delayed. I would appreciate either a replacement coffee at no charge or a credit toward my bill for the price of the coffee.
Proportional requests show maturity and sound reasonable. Over-the-top requests make your letter look like a rant, not a legitimate complaint. Band 7 writers stay calm and measured.
After you finish your letter, don't just read it once. Walk through this checklist:
Five minutes. Do this and you'll catch 80% of argument strength problems before you submit.
Let's work through how this applies to actual Task 1 prompts and how an IELTS essay checker would evaluate them.
Task prompt: You recently stayed at a hotel and were disappointed with the service. Write a letter to the manager.
Band 6 version: I stayed at your hotel last month and the service was terrible. The staff were not helpful and the room was cold. I paid a lot of money and expected better. I think you should train your staff better and check the heating system. Please let me know what you will do about this.
Why it's weak: No dates, no specifics, no cause and effect. The reader doesn't know when you stayed, which staff member was unhelpful, or what they did wrong. "Cold room" could mean anything. How cold? For how long? The request is vague too. "Let me know what you will do" is passive and unclear.
Band 7 version: I am writing to express my disappointment with my stay at your hotel from 5–8 November. Upon arrival, I requested assistance with the heating in Room 312, as the temperature was approximately 12 degrees Celsius. The receptionist promised to send maintenance within one hour, but no one arrived until the following morning. As a result, I spent an uncomfortable night and missed part of the next day's business meeting due to fatigue. Given this failure to address a basic guest need promptly, I would appreciate either a partial refund of my accommodation fees or a complimentary night's stay on a future visit.
Why it's strong: Dates, room number, specific temperature, timeline of what was promised versus what happened, direct consequence, proportional request. The cause and effect is unmissable. This is the kind of letter an IELTS writing correction service would rate highly for Task Response.
Task prompt: Write a letter to a language school requesting information about their courses.
Band 6 version: I am interested in your courses. Can you tell me about the programs you offer? How long are the courses? What is the cost? How often are classes? Please send me more information.
Why it's weak: No context. Why does the writer want this information? What's their English level? What's their goal? The school can't give a targeted answer to generic questions. The argument for why they should prioritize responding is invisible.
Band 7 version: I am writing to request information about your intermediate English programs. I am relocating to your city in February for a six-month work assignment and need to improve my professional communication skills, particularly in presentations and written reports. I would like to know the following: do you offer part-time evening courses, are there intensive weekend options, what is the total cost including materials, and when do the next intake dates begin? I would be grateful if you could send me a course schedule and pricing information at your earliest convenience.
Why it's strong: The writer provides context that helps the school understand who they're dealing with (relocation, work assignment, six-month timeline). The specific goals (presentations, reports) show they're serious. The questions are targeted to their situation. The tone is professional. The school now knows exactly how to help.
Pro tip: In request letters, argument strength comes from showing why you deserve a response. Vague requests get ignored. Specific, relevant requests get answered. A Band 7 writer makes it easy for the recipient to help them.
These five mistakes show up in almost every Band 6 letter:
Task 1 requires 150 words minimum. You can write 180 or 220. But here's what most students get wrong: they pad weak arguments with extra words instead of making the arguments strong.
A Band 6 letter might hit 170 words and still be weak because 40 of those words are just filler. A Band 7 letter might be 165 words and strong because every single word serves the argument.
Common filler: "As I mentioned earlier," "It is very important," "In my opinion I think," "I would like to point out." These add word count without adding force.
Strong phrases: "According to your website," "As outlined in your rental agreement," "This resulted in," "Consequently." These add both word count and argument power.
When you check your letter, ask: does this word help prove my point or explain my situation? If not, delete it. Then add a fact or connection instead.
Argument strength isn't separate from tone. A rude letter weakens your argument even if your facts are solid. Keeping the right formality level without sounding robotic is key to moving from Band 6 to Band 7. Get the tone right and your argument lands harder.
An IELTS writing checker can spot argument strength problems you might miss on your own. The best ones flag three things: vague claims, missing evidence, and disconnected reasoning. When you run your letter through a checker, look for:
Using a free IELTS essay checker regularly trains your eye to spot these issues yourself, which is what examiners reward.
Use our free IELTS writing checker to evaluate your letter's argument strength, spot vague claims, and get instant feedback on your band score. See exactly which sentences weaken your response and how to fix them.
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