Your letter starts with "Hey mate, hope you're doing alright." The examiner reads it. Instantly, 2 band points vanish.
That's not hyperbole. Tone and register mistakes in IELTS Task 1 letters cost you way more than you realize. You might nail grammar and communicate your ideas clearly, but if your salutation sounds like you're texting a friend when the task demands formality, examiners dock you on Task Response and Lexical Resource. This is where most students stumble, and the good news? It's completely fixable with an IELTS writing checker or by learning to spot these mistakes yourself.
In this post, you'll learn exactly how to spot when a letter needs to be formal or informal, which words to ditch or embrace, and how to catch register mistakes before they tank your band score.
Let's talk numbers. IELTS Writing is 40 points total across Task 1 and Task 2. Task 1 counts for about 40% of that score. Within Task 1, examiners grade you on four criteria: Task Response, Coherence and Cohesion, Lexical Resource, and Grammatical Range and Accuracy.
Register mistakes hurt two of those criteria directly. Task Response takes a hit because you haven't matched the tone the task requires. Lexical Resource drops because you're using informal vocabulary in a formal context, or vice versa. That's not a small penalty.
Here's why it happens. Most students learn "formal writing" and think it means sounding stiff and unnatural. They write things like "I am writing to inform you" when "I'm writing about my damaged laptop" works better and sounds less robotic. Or they swing the other way and use slang because they think that's how people actually talk. Both are register fails.
Tip: Register isn't about using fancy words. It's about matching the social distance between you and the reader. You'd complain to a friend differently than you'd complain to a company. IELTS wants you to show you know the difference.
IELTS General Training gives you two basic letter scenarios. You're writing either to someone you know (friend, family member) or someone you don't (company, landlord, council official). This determines everything about how your letter should sound.
Letters to people you know should sound conversational but not careless. Contractions are fine. You can be warm and friendly. You can ask casual questions. But you're still writing a formal document, not a text message. Your reader expects clarity and respect.
Letters to strangers or organizations must be professional. No slang. No overly casual language. You're solving a problem or making a request, and your tone should show you take it seriously.
Most failed Task 1 letters make one mistake: they sound too stiff when writing to people they know, or way too casual when writing to formal contacts. The task prompt tells you exactly who you're writing to. Read it twice before you start.
Your opening and closing lines set the register for everything in between. Get these wrong, and you've already signaled to the examiner that you don't understand the tone you need.
Formal letter salutations (to unknown recipients, organizations, officials):
Semi-formal letter salutations (to people you know but want to sound respectful):
Informal letter salutations (to friends, close contacts):
Notice "Dear [Name]" shows up in all three. That's deliberate. It's safe and correct in any situation. Stick with it if you're ever unsure.
Now for closings. This is where people really mess up.
Formal letter closings:
Semi-formal or friendly letter closings:
Informal letter closings:
Weak: "Hi mate, I'm writing because I'm not happy with the service your company gave me. Catch you later, mate."
Good: "Dear Sir or Madam, I am writing to lodge a complaint regarding the poor service I received. I look forward to your response. Yours faithfully, [Name]"
The first example throws "mate" and "catch you later" at a company. Instant register fail. The second is formal, clear, and hits the right tone.
Informal words kill formal letters faster than any other mistake.
When you're writing to a company or official, avoid these informal words and phrases:
Use these formal alternatives instead:
Here's the trap: formal doesn't mean you have to sound like a robot from the 1980s. You don't need to say "I am writing to bring to your attention" when "I'm writing about a problem with my booking" works perfectly and actually sounds more natural.
Weak: "I hope this letter finds you in a state of good health and positive spirits."
Good: "I hope you're well." (Or skip the pleasantries and start with your purpose: "I'm writing about my damaged passport.")
Examiners grade you on Task Response and Lexical Resource. Natural formal writing beats forced formality every single time. Aim for professional clarity, not outdated drama.
This trips up a lot of students. Can you use contractions in formal letters? The answer is: probably not, but it depends.
In a letter to your bank about a missing payment, "I'm concerned" reads strangely. "I am concerned" is safer and sounds more formal. But in a friendly letter to someone you know well, "I'm looking forward to your reply" is totally fine.
The safest rule: skip contractions in formal letters to people you don't know. Use them sparingly in semi-formal letters to people you do know. This one choice alone boosts your band score because it shows you understand register.
Tip: When you're unsure, write it out. "I am" takes two more characters than "I'm" and signals formality. In a timed exam, that tiny choice adds up in band points.
Mistake 1: Mixing formal and informal in the same letter.
Weak: "Dear Sir or Madam, I'm really annoyed because your staff was being rude to me. I want you to fix this ASAP. Cheers, [Name]"
This opens formal but drops to casual mid-letter ("really annoyed," "ASAP," "Cheers"). Pick one register and stick with it.
Mistake 2: Assuming formal always means complicated.
Weak: "I hereby beseech your esteemed organization to acknowledge the receipt of my correspondence regarding the aforementioned deficiency."
That's not formal. That's archaic and awkward. You'll lose marks for sounding unnatural. Formal means clear, direct, and professional.
Good: "I am writing to inform you that I received a damaged item in my order."
Mistake 3: Using slang or very informal language in letters to friends.
Weak: "Hey fam, so like I can't make it to your party cos something came up lol. My bad. C u soon!"
Even in informal letters, you're writing a structured letter, not a text. The tone can be warm and relaxed, but it shouldn't read like Snapchat.
Good: "Hi Sarah, I'm sorry, but I can't make it to your party next Saturday. Something unexpected came up. I hope you understand. Let's catch up soon. All the best, [Name]"
Before you submit, run through this quick checklist. You'll catch register mistakes in seconds.
That whole process takes 90 seconds. In a 20-minute writing slot, that's a smart investment because it catches about 80% of register mistakes before the examiner ever sees them.
Tip: If you're unsure whether a word fits your tone, it probably doesn't. Replace it with something you're confident about. Examiners reward confidence in register.
Let's look at actual IELTS-style prompts and the right register for each.
Example 1: Informal letter to a friend
"You have a friend who lives in another country. Write a letter telling your friend about an interesting event that happened in your town. Include details about what happened and why you found it interesting."
Register: Warm, conversational, personal. You can use contractions. You can ask questions. But keep it structured like a real letter.
Example 2: Formal letter to an organization
"You are unhappy about a recently purchased electronic item. Write a letter to the shop manager. Explain what is wrong with the item and what action you would like the shop to take."
Register: Professional, direct, solution-focused. Avoid contractions unless absolutely necessary. No slang. Make your problem statement clear and your request specific.
Example 3: Semi-formal letter to an acquaintance
"You have borrowed a book from a colleague. You have now finished reading it. Write a letter to return the book. Explain what you thought of the book and suggest another book your colleague might enjoy."
Register: Friendly but respectful. You can say "Hi [Name]" and use contractions, but keep it professional enough to show you value the relationship.
Notice how the prompt itself hints at register. "Tell your friend" signals informal. "Write to the manager" or "Write to an official" signals formal. Learn to spot those cues in the task instructions. If you need help catching tone issues, use our free IELTS writing checker to evaluate your letter's register and get instant feedback before test day.
You've written your letter. You've got 2-3 minutes left. Use them to catch tone shifts and register errors before submission. Our IELTS writing checker flags formal-informal mismatches, inappropriate vocabulary choices, and salutation problems automatically. You get specific feedback on whether your letter's tone matches the task requirements. Try our free IELTS writing correction tool to see exactly where your register needs adjustment.
Use our IELTS writing evaluator to catch tone and register mistakes before test day. Get instant feedback on formality, vocabulary choices, and your band score prediction.
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