Here's the thing. You can write a grammatically perfect IELTS Task 1 letter and still walk away with Band 6 instead of Band 7. Why? Your arguments don't convince anyone.
Most students treat Task 1 like a checklist. They write what the prompt asks for, but they don't actually persuade. They don't give specific details. They don't build a case. This is where most students stumble, and it costs them 1 to 2 band points in the Task Response criterion—which counts for 40% of your writing score.
In this post, I'll walk you through exactly how to evaluate your own letter arguments before you hit submit. You'll learn the three things that separate Band 6 from Band 7, see side-by-side examples of weak versus strong arguments, and get a checklist you can use on every formal letter you write.
The IELTS Writing Band Descriptors don't use the word "argument" for Task 1. They talk about "task response" and "appropriate tone" and "organisation." But here's what they're really checking: does this letter convince someone to care?
For Band 7, the descriptor says you need ideas that are "clearly presented and well-developed." For Band 6, ideas are "presented adequately." That gap matters. Well-developed means you've given reasons, examples, or context. Adequately presented means you've just stated the basic fact and moved on.
Band 7 also requires "fully appropriate register," which means your tone and formality match your reader. A complaint to a manager needs to sound professional but firm. A request to a friend feels warmer. Your argument's strength depends partly on choosing the right tone for that specific person.
Most Band 6 letters skip this entirely. They use the same formal, stiff tone for every letter. They mention a problem once and hope the reader gets it.
Every Band 7 argument in Task 1 rests on three things: specificity, evidence, and reader acknowledgment.
Pillar 1: Specificity. Don't say "the service was bad." Say what exactly went wrong, when, and who was involved. If you can, add dates, names, or reference numbers. If you can't, be specific about what happened instead.
Pillar 2: Evidence. Back up your claim with one concrete detail. This might be something you experienced, something you observed, or a logical result. Your main points need evidence. Not every sentence does.
Pillar 3: Reader acknowledgment. Show you understand the reader's position or constraints. This turns your argument from complaining into persuading. You're finding common ground.
Let's see how this works in real letters.
Take this IELTS Task 1 prompt: "You recently bought an expensive item (a smartphone, laptop, or piece of furniture) that stopped working after two weeks. Write a letter to the shop manager demanding a refund or replacement."
Weak: "I bought a laptop from your shop two weeks ago. It is broken now. I am very upset. I want a refund. The product quality is bad. Please refund my money as soon as possible."
What's missing? Everything. No specificity: which laptop model? What day did you buy it? How exactly is it broken? No evidence: what happens when you use it? No acknowledgment of the reader: is the manager responsible for quality? Does the shop have a return policy? The argument is just complaints with nothing to back them up.
Strong: "On July 10th, I purchased an ASUS VivoBook 14 (model X1405VA, £549) from your Bristol branch. Within two weeks, the keyboard stopped responding intermittently, making basic typing impossible. I've used the device carefully and have the original receipt and warranty card. I understand your shop's 30-day return policy covers manufacturing defects, and I would appreciate either a full refund or an exchange for a replacement unit. I'm available for inspection on weekday afternoons if that would help."
See the difference. Specific details: model number, purchase date, price, location, what exactly went wrong. Evidence: "keyboard stopped responding intermittently" tells the manager precisely what's broken. Reader acknowledgment: "I understand your shop's 30-day return policy" shows you've done your homework and you're asking within the terms. Tone: professional and reasonable, not just angry.
The strong version scores Band 7 for Task Response. The weak version sits at Band 5 or 6 because the argument doesn't persuade and doesn't give the reader enough information to act on it.
Here's another prompt: "You're planning to study abroad and need a reference letter from your university professor. Write a formal letter requesting this."
Weak: "Dear Professor, I need a reference letter for my studies abroad. Could you write one for me? I was a good student in your class. I took your course last year and got good grades. I hope you can do this for me soon. Thank you."
The argument for compliance is thin. "I was a good student" isn't evidence. Why should the professor remember you or prioritize your request? There's nothing that shows you understand this takes their time.
Strong: "I am writing to request a reference letter for my postgraduate applications to engineering programmes in Canada. I completed your Advanced Thermodynamics module in Spring 2025 and received a final grade of 85, which was among the highest in the cohort. I believe your perspective on my technical understanding would strengthen my application, particularly because the university emphasises practical problem-solving skills, which you emphasised throughout the course. I understand this is a time-consuming task, so I would be happy to provide a draft outline or additional materials to assist you. The deadline is September 15th, and I'm available to discuss this further at your convenience."
Here's what works: specific context (module name, grade, semester), proof of your performance (among the highest in cohort, specific skills you learned), reader acknowledgment (recognizing the time and effort involved), and practical help (offering to provide materials). You've made it easy for the professor to say yes because you've shown respect and given them everything they need.
Be honest about this. The IELTS examiner doesn't care about your feelings. They care about whether your letter is convincing and appropriate. That means evidence, not emotion.
Look at this phrase that shows up in roughly 30% of Band 6 complaint letters: "I was extremely disappointed with the service." This tells the examiner how you felt. It doesn't tell them what happened or why they should care. Compare it to: "On three separate visits, staff failed to address the issue I had reported in writing, despite the service agreement's 48-hour response time." Now they understand the problem, its pattern, and why it matters.
Here's a quick test for your own letter. Read each paragraph and ask yourself: "If someone asked me 'how do you know that?' could I answer in one sentence?" If you can't, your argument needs more development.
Tip: Go through your draft and highlight every claim you make. For each claim, add one piece of evidence in the next sentence. This doesn't mean every sentence needs evidence, but your main arguments do. This single change often pushes you from Band 6 to Band 7 on Task Response.
A strong argument uses the right tone. Task 1 examiners check "appropriately maintains register," which means you sound like you're writing to that specific person in that specific situation.
Here's where students go wrong: they assume "formal" means "stiff." So they write the same neutral, distant tone to their landlord, their professor, and a company customer service team. But the register should change depending on who's reading it.
A complaint to a company manager can be assertive and direct. A request to a university professor should be deferential. A letter to a council about a community issue should be civic-minded and collaborative. Your argument's tone needs to fit what works for that reader.
Compare these two openings for a complaint letter:
Weak tone: "I am writing to inform you of a significant issue. Your company has provided inadequate service. This is unacceptable."
This sounds like you're scolding them. The register is too formal and slightly condescending, which doesn't persuade.
Strong tone: "I am writing to request your assistance with an order that has encountered a significant issue. Your company's service has fallen short of what I would reasonably expect, and I would like to work with you to resolve this."
This is professional and assertive without being rude. You're treating the manager as someone capable of helping, not blaming them personally. You're inviting collaboration. That's the tone that gets results.
Spotting weak arguments in your own writing is harder than spotting them in examples. That's where an IELTS writing checker helps. A good tool evaluates your Task 1 letter against the official band descriptors and flags weak arguments, vague evidence, and tone issues before you submit.
When you use an IELTS letter argument checker, look for feedback on specificity. Does it tell you which claims need more detail? Strong feedback highlights exactly where you've been vague. It should also evaluate evidence quality across your main points. A reliable IELTS essay checker or letter evidence evaluator will show you which arguments feel thin and which feel solid.
Our IELTS writing correction tool does exactly this for Task 1 letters. Check your letter with our free IELTS writing checker to get instant feedback on whether your arguments will convince an examiner.
Here's a practical tool you can use right now. Before you finish any Task 1 letter, run through this checklist. Each yes keeps you in the Band 7 zone; each no pulls you back toward Band 6.
If you've ticked at least five of these, you're likely at Band 7 for Task Response. If you've ticked three or fewer, you need to revise.
You'll see the same errors in Band 6 letters over and over. Here are the top three that cost you points.
Mistake 1: Stating the problem without context. "Your staff was rude." This doesn't persuade. What did they say or do? When? Was there a reason? Band 7 answers these in one or two sentences. Band 6 just complains and moves on.
Mistake 2: Making demands without justification. "I want a full refund immediately." Why do you deserve this? What does your purchase agreement say? Did you try other solutions first? Band 7 letters build a logical case. Band 6 just demands.
Mistake 3: Ignoring reader perspective. The best arguments acknowledge the reader's side, even if you disagree. "I understand staffing is tight, but..." or "I recognise your time is limited, however..." This makes you sound fair and reasonable. Band 6 letters sound self-centred because they don't do this.
Tip: When you revise, read your letter aloud as if you're the person receiving it. Does it persuade you? Does it sound reasonable? Does it give you enough information to act? If you answer no to any of these, your argument isn't strong enough yet.
Not all evidence is equal. "I was unhappy" is not evidence. "The temperature dropped to 15 degrees Celsius despite the thermostat setting of 22 degrees" is evidence. One is vague feeling; the other is measurable fact.
For Task 1, you have four types of evidence you can use: personal observation, numbers or dates, logical consequence, and external context.
Personal observation: "I noticed the paint was chipped along the entire left edge of the window frame."
Numbers or dates: "This has happened three times in the past two months, most recently on July 22nd."
Logical consequence: "As a result, rain now leaks through the gap, which has damaged the floor underneath."
External context: "According to your company's website, all installations come with a five-year structural guarantee."
A Band 7 letter uses at least two of these in the body paragraphs. A Band 6 letter often uses none, just restates the basic problem. When you check your own work, highlight each piece of evidence in a different colour. If you see mostly blank space, you need more evidence.
You know what separates a Band 6 letter from a Band 7 now: specificity, evidence, and reader acknowledgment. But spotting these gaps in your own writing is harder than spotting them in examples.
Use our IELTS writing checker to evaluate your Task 1 letter against the official band descriptors. You'll get instant feedback on exactly what to fix before you submit.
One more thing worth mentioning: your closing statement can either reinforce or undermine all the argument work you've done. If you've built a strong case with evidence and reader acknowledgment, but your closing sounds desperate or rude, you lose Band 7 points on register. Learn exactly how to end a Band 7 letter in our guide on closing statements for formal letters.
For more guidance on IELTS writing corrections and band score improvement, explore our band score guides and essay topics practice. You can also use our band score calculator to track your progress across all criteria.