Here's the thing: you can write a technically perfect letter. Your grammar is flawless. Your vocabulary is sophisticated. Your structure is clean. And you'll still lose points.
Why? Because you've misidentified what type of letter the question is asking for, and you've answered the wrong purpose.
This happens to roughly 15-20% of IELTS test takers, and it tanks the Task Response band descriptor, which counts for 25% of your Writing Task 1 score. Let me be blunt: if the examiner thinks you've written a formal complaint letter when they asked for an informal request, you're capped at Band 6, no matter how well you write.
This guide teaches you how to identify letter purpose correctly every single time, and how to use that to protect your band score.
The IELTS Writing Task 1 band descriptors explicitly measure Task Response. That means the examiner is asking one question: did the candidate write what was actually asked for?
A Band 8 response "fully satisfies all the requirements of the task". A Band 6 response "addresses the task but not all aspects are fully covered". A Band 5 response "addresses the task but incompletely".
Misidentify the letter purpose, and you've instantly failed to cover the task completely. Your band score reflects this the moment the examiner reads your opening line.
The three things examiners check in Task Response are:
Get the purpose wrong, and you fail all three at once.
The prompt itself gives you signals. You just need to read for them.
Formal letter signals: The recipient is a stranger, an organization, or someone in authority. You'll see words like "company", "manager", "authority", "organization", "official", or "formal complaint". You've never met this person. You don't know their first name.
Informal letter signals: The recipient is a friend, family member, or someone you know personally. The prompt says "write to your friend", "your cousin", "someone you know", or describes a personal relationship. The tone is casual or conversational.
Here's a real IELTS example to anchor this:
Example prompt (FORMAL): "Write a letter to the manager of a hotel where you stayed last week. Complain about the poor service. Explain what went wrong and what you want the manager to do about it."
The word "manager" signals a stranger. The context (complaint to a business) confirms formality. You don't sign off with "Love" or use contractions loosely.
Example prompt (INFORMAL): "Write a letter to a friend who has invited you to stay with them next month. Explain why you cannot come. Suggest an alternative time to visit."
The word "friend" signals personal relationship. You can use contractions, casual phrasing, and a warm tone. The content is about your life, not a service complaint.
Here's a trickier one that catches students out:
TRAP prompt: "Write a letter to your teacher about a problem you had with your course. Explain the problem and ask for help."
Is this formal or informal? Your teacher is someone you know, but it's still a position of authority about an academic matter. This is semi-formal. You use "Dear [Name]" or "Dear Sir/Madam", but you can be slightly warmer than a pure business complaint. You're not writing to "my mate" but you're addressing someone in a position of responsibility.
Once you've identified the letter type, everything else shifts. Your vocabulary, sentence structure, and politeness all have to match. This is what "register" means.
Formal letter characteristics: No contractions (write "do not" instead of "don't", "cannot" instead of "can't"). Indirect requests. Polite, measured language. Standard opening (Dear Sir or Madam / Dear [Name]). Standard closing (Yours faithfully / Yours sincerely / Kind regards).
Informal letter characteristics: Contractions are fine (don't, can't, won't). Direct requests. Casual, warm language. Relaxed opening (Hi [Name], Hey [Name]). Relaxed closing (Cheers, Best, All the best, Talk soon).
Let's see this in action:
Weak (formal letter written informally): "Hi Sir, I'm writing because the hotel was really bad. The staff weren't helpful and the room was dirty. Can you please give me my money back? Thanks a lot."
This fails because it's a formal complaint using informal tone. "Hi Sir" mixes registers awkwardly. Contractions in a business letter look unprofessional. "Thanks a lot" is too casual for a complaint.
Good (formal letter with correct register): "Dear Manager, I am writing to lodge a formal complaint regarding my recent stay at your hotel. The staff were unhelpful and the room was not clean. I would appreciate a full refund of my booking. Yours sincerely, [Name]"
This works because it uses the formal register consistently. "Lodge a complaint" is assertive. "Would appreciate" is polite but not desperate. Full forms throughout. Proper closing.
Now the opposite error:
Weak (informal letter written formally): "Dear Friend, I hope this letter finds you in good health. I am writing to inform you that I am unable to attend your gathering next month. I would be most grateful if we could reschedule our meeting. Yours faithfully, [Name]"
This fails because you sound like a robot writing to a friend. "I am unable to attend your gathering"? You would never say that to someone you know. "Yours faithfully"? That's for business letters. It's grammatically correct but tonally wrong.
Good (informal letter with correct register): "Hi Sarah, Thanks so much for the invite to stay next month. I really wish I could come, but I've got that work project on. Could we maybe reschedule for next spring instead? Let me know. Cheers, [Name]"
This works because the tone matches the relationship: casual, warm, direct, and personal.
Stop guessing. Use this process every time you see a Task 1 letter prompt.
Step 1: Read the recipient. Who are you writing to? A stranger, an organization, or someone you know? If you had to describe this person in one word, would it be "friend", "family", "boss", or "stranger"?
Step 2: Read the context. Is this a personal matter (social, life updates, relationships) or a professional matter (complaints, applications, official business)? Does the prompt use words like "manager", "company", "official", or does it use "friend", "invite", "personal"?
Apply both filters, and your letter type becomes obvious. The moment you answer these two questions, your register decision should be automatic.
Tip: Write the letter type at the top of your practice page before you start writing. It sounds simple, but it forces you to commit to an answer and keeps you accountable. If you write "FORMAL COMPLAINT TO MANAGER" in caps, you're less likely to slip into casual tone halfway through.
Mistake 1: Semi-formal letters treated as fully informal.
A letter to your teacher, coach, or someone in a mentoring role is semi-formal, not informal. You know them, but there's authority involved. Use "Dear [Name]" not "Hi [Name]", and avoid overly casual language like slang or excessive contractions. This is where the band score gets docked: students write like they're texting a friend, when actually they need to show respect for the person's position.
Mistake 2: Formal letters given an informal tone because the content feels personal.
You're writing a complaint about a delayed delivery, a request for a refund, or an inquiry about a job you applied for. Because it's about your own situation, students sometimes write informally. But the recipient is still unknown to you, and it's still a formal context. Your personal stake in the matter doesn't change the register. Stay formal.
Mistake 3: Not distinguishing between a "request" and a "complaint".
These are both formal, but they carry different tones. A request is polite and hopeful: "Would it be possible to..." A complaint is assertive and direct: "I am writing to lodge a complaint..." If you confuse these, your tone will be off. Read the prompt carefully. The words "complain", "dissatisfied", "unhappy", "problem" signal complaint. The words "ask", "request", "inquire", "suggest" signal a request.
Let's attach real numbers to this.
The Task Response band descriptor for Writing Task 1 is divided across bands like this:
Misidentify the letter purpose and you have failed to fully address the task. That caps you at Band 6 maximum, even if everything else is perfect. Your Coherence & Cohesion might be Band 8, your Grammatical Range might be Band 8, but Task Response keeps you at Band 6.
For context, Band 6 is 6.0 on one section. If all your other writing sections are Band 8, a single Band 6 in Task Response tanks your Writing score to roughly 6.5-7.0 instead of 7.5-8.0.
That is the difference between a competitive Band 7 application and a marginal one.
When you are under time pressure (45 minutes for Task 1), you need to recognize purpose signals fast.
Red flags for FORMAL:
Red flags for INFORMAL:
Red flags for SEMI-FORMAL:
The moment you see these phrases, your letter type decision should be automatic.
Do not just write letters. First, practice identifying purpose without writing anything.
Take 10 Task 1 letter prompts. For each one, before you write, write down:
Do this for 10 prompts, checking your answers against model solutions or a band score guide. You will start seeing the patterns. The patterns are not subtle. Formal letters have formal prompts. Informal letters have informal prompts. Once you train your eye, you will stop missing these.
Then, write the letters. When you are done, check: did your tone match your identified purpose? If you identified it as formal but used "Hi mate" in the opening, you have found your problem.
If you are working on avoiding tone shifts mid-letter, this same practice catches those errors too. The more you commit to a register decision upfront, the more consistent your letter becomes.
Even when you think you have nailed the letter purpose, a tiny register slip can still cost you. A single "don't" in a formal letter, or one overly stiff sentence in an informal one, and the examiner starts questioning whether you really understood what was asked.
That is why it helps to use an IELTS writing checker before test day. You get instant feedback on whether your tone matches your letter type, and you see exactly where register slips happen. You will catch the mistakes that your own eyes miss, especially when you are tired after writing Task 2.
An IELTS essay checker also flags other common Task 1 errors like number misrepresentation and weak closing paragraphs. Combined with purpose identification, these are the three biggest band score killers in Task 1.
Your writing will improve faster with feedback on every letter you practice. Each checker report shows you exactly where your register breaks down, so you learn the patterns and stop repeating the same mistakes.
Get instant feedback on letter purpose, tone, register, and other band score mistakes before your exam.
Check My Essay Free