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Letter writing is something I see my students struggle with more than they expect to. It’s not just about what you say — it’s about matching your tone and structure to your reader and the situation. The same message written to a friend reads completely differently when it’s addressed to a job interviewer. I’ll show you the one framework that works for both informal and formal letters, plus the exact phrases that signal which register you’re using.
By the end, you’ll understand exactly when to use contractions, which opening lines work for strangers versus friends, and how to format your letter so it looks professional. You’ll also have four complete sample letters to reference whenever you’re unsure.
Key Takeaways
- Informal letters use first names, contractions, and conversational tone — right for friends and family.
- Formal letters use titles + surnames, full grammar, and professional tone — required for business and academic contexts.
- Structure matters — formal needs your address, date, and subject line; informal just needs a greeting and closing.
- The register test — if you’d wear a suit to meet this person in real life, write them a formal letter.
- Opening and closing lines are the signal — “Dear Ms. Kim” vs. “Hey Sarah” tells the reader everything they need to know.
The Core Difference: Register
English letters fit into two main registers: informal (personal letters to people you know) and formal (business, academic, professional letters to strangers or people in authority). The register you choose affects every word—from your greeting to your closing signature.
Think of register as a spectrum with two poles. At one pole (informal), you’re relaxed, you use abbreviations, you might use slang. At the other (formal), you’re precise, respectful, and follow strict formatting rules. Most professional contexts demand the formal pole; most letters to friends live comfortably at the informal pole.
Informal Letter Writing
Structure of an Informal Letter
Informal letters are simpler to structure than formal ones. You don’t need your address, the date isn’t critical, and there’s no subject line. Here’s what you do need:
- Greeting: “Dear [Name],” or just “Hi [Name],”
- Opening line: A warm, personal sentence that references your relationship or last contact.
- Body: Share news, ask questions, build the conversation naturally.
- Closing: A friendly sign-off like “All the best,” or “Take care,” followed by your first name.
Example structure:
Hi Maria,
Hope you’ve been well! I wanted to tell you about my new job — I’m really excited about it.
How have you been? Are you still working at the marketing firm? I’d love to catch up over coffee sometime soon.
All the best,
James
Informal Letter Language
In informal letters, you can and should use:
- Contractions: “I’m,” “you’ve,” “don’t” — these make you sound like yourself.
- Casual vocabulary: “pretty cool,” “I’m swamped,” “that’s awesome.”
- Conversational structures: Short sentences, fragments for emphasis, natural flow.
- Personal pronouns: “I,” “we,” “you” — informal letters are about connection.
- Emotion words: “I felt terrible when I heard,” “I’m so happy for you.”
Sample Informal Letter
Dear Sam,
Thanks so much for the birthday gift — the book you picked out is brilliant, and I’ve already started reading it. I can’t believe you remembered my favorite author!
I’ve been meaning to reach out because I wanted to tell you about my new apartment. I finally found a place close to work, so I won’t have to spend two hours commuting anymore. You’ll have to come over once I’ve got the furniture sorted.
How’s the new job treating you? Last time we talked, you seemed stressed about the transition. Let me know how it’s going when you get a chance.
Hope to see you soon,
Alex
Formal Letter Writing
Structure of a Formal Letter
Formal letters follow a strict format. Every element has its place, and skipping one signals carelessness. Here’s the order:
- Your address: Your street address, city, postal code.
- Date: The date you’re writing the letter (e.g., 23 April 2026).
- Recipient’s address: The full name, title, company, and address of the person you’re writing to.
- Greeting: “Dear Sir/Madam,” “Dear Mr. Chen,” or “To Whom It May Concern,” (formal only).
- Subject line (optional but recommended): A one-line summary of your letter’s purpose.
- Body: Introduction, main content, conclusion — three clear paragraphs minimum.
- Closing: “Yours sincerely,” “Sincerely,” or “Best regards,” followed by your typed name.
Formal letter example layout:
123 Main Street
London, UK SW1A 1AA23 April 2026
Ms. Sarah Chen
Senior Manager
ABC Marketing Inc.
456 Business Avenue
London, UK E1 6ANDear Ms. Chen,
Subject: Application for Marketing Manager Position — Ref. JO-2026-445
I am writing to express my strong interest in the Marketing Manager position advertised on your company website. With seven years of experience in digital marketing and a proven track record of building successful campaigns, I believe I am an ideal fit for your team.
[Body paragraphs with details]
I would welcome the opportunity to discuss how my skills can contribute to ABC Marketing’s continued success. Thank you for considering my application. I look forward to hearing from you at your earliest convenience.
Yours sincerely,
James Wilson
Formal Letter Language
In formal letters, you avoid:
- Contractions: Never use “I’m” or “don’t” — write out “I am” and “do not.”
- Slang or colloquialisms: Don’t write “pretty cool” or “swamped” — use “impressive” and “heavily committed.”
- Exclamation marks: Use them sparingly, if at all — formal tone prefers periods.
- Casual abbreviations: Write “et cetera” or “and so on,” not “etc.” — and never start sentences with “BTW” or “FYI.”
- Emoji or symbols: Keep text-only, completely professional.
Sample Formal Letter
42 Oxford Street
Cambridge, UK CB2 1QJ15 March 2026
Dr. Michael Patterson
Head of Human Resources
Trinity Education Limited
500 Enterprise Drive
Cambridge, UK CB1 0AADear Dr. Patterson,
Subject: Request for Reference — Teaching Position Application
I hope this letter finds you in good health. I am writing to request your assistance in providing a professional reference for my application to a teaching position at Exeter Secondary School. Given your five years of supervision of my work as an Education Coordinator at Trinity, I believe your reference would substantially strengthen my candidacy.
I have attached a copy of my curriculum vitae and the job description for your reference. The position requires a reference from a former supervisor, and I would be grateful if you could complete the enclosed reference form by 31 March 2026.
Thank you for taking the time to consider this request. I appreciate your support and look forward to your response.
Yours sincerely,
Emma Richardson
Do’s and Don’ts Comparison
| Aspect | Informal Letter | Formal Letter |
|---|---|---|
| Greeting | ✓ “Hi Sarah,” / “Dear Tom,” | ✓ “Dear Mr. Kim,” / ✗ “Hi there” |
| Contractions | ✓ “I’m,” “you’ve,” “can’t” | ✗ Never — use “I am,” “you have,” “cannot” |
| Your address | Optional — not always needed | ✓ Always required at top |
| Tone | ✓ Warm, relaxed, personal | ✓ Professional, respectful, neutral |
| Sign-off | ✓ “Take care,” “All the best,” “Love,” | ✓ “Yours sincerely,” “Best regards,” |
| Exclamation marks | ✓ One or two OK for warmth | ✗ Avoid; use periods instead |
| Emotions | ✓ Show feelings freely | ✓ Professional warmth only |
| Length | Can be brief and casual | Should be concise but complete |
Common Mistakes Learners Make
✗ Incorrect: “Hi, Mr. Chen! I hope your doing great. I wanted to ask about the job opening — can I send you my resume?”
✓ Correct: “Dear Mr. Chen, I hope this letter finds you well. I am writing to inquire about the job opening. Please find my resume attached.”
Why: Mixing registers — “Hi” is too casual for formal, contractions don’t belong, and “your” should be “you’re”.
✗ Incorrect: “Dear Valued Customer, I appreciate your business. Your account is very important to our company and we want to thank you for everything.”
✓ Correct: “Dear Valued Customer, I appreciate your business. Your account is important to our company, and we want to thank you for your continued loyalty.”
Why: Repetition of “very important” → use one strong adjective instead.
✗ Incorrect: “I’m writing because I don’t know what to do about my grades. Could you possibly maybe help me figure this out?”
✓ Correct: “I am writing to request a meeting to discuss my recent grades and explore strategies to improve my performance.”
Why: Contractions belong in informal; formal requires “I am.” Also, be direct, not tentative.
Email vs. Traditional Letter
Today most professional communication happens in email, but the register rules still apply. An email to a new client should be as formal as a traditional letter; an email to a colleague you know well can be informal. The medium changed—the rules didn’t.
Formal email: “Dear Ms. Patel, I am writing to follow up on our conversation regarding the proposal…”
Informal email: “Hi Maya, Hope you’re having a good week! I wanted to follow up on the project we discussed…”
Sample Dialogue: Register Mix-Up
Teacher: Lucas, I read your letter to the university admissions office. It started “Yo, what’s up?” — that’s not appropriate.
Lucas: But I was trying to sound natural, like myself.
Teacher: I understand, but this is a formal letter to a stranger in authority. You can sound like yourself while still being professional. Try: “Dear Admissions Officer, I hope this letter finds you well.”
Lucas: So I can’t be myself?
Teacher: You can. But different situations call for different voices. When you’re talking to your friends, you’re authentic. When you’re writing to a university, being professional doesn’t make you fake — it makes you respectful.
Quick Quiz
Which greeting and closing match the situation?
- You’re writing to your old university professor about a reference for a job application. → Opening: ________ / Closing: ________
- You’re writing to your cousin to catch up after six months. → Opening: ________ / Closing: ________
- You’re emailing a potential employer whose name you don’t know. → Opening: ________ / Closing: ________
- You’re writing a thank-you note to a friend who gave you a birthday gift. → Opening: ________ / Closing: ________
- You’re writing to your HR department about a payroll issue. → Opening: ________ / Closing: ________
Answers: 1. “Dear Professor [Name],” / “Yours sincerely,” · 2. “Hi [Name],” / “All the best,” · 3. “To Whom It May Concern,” / “Best regards,” · 4. “Dear [Name],” / “With thanks,” · 5. “Dear HR Team,” / “Best regards,”
Related Articles
- How to Write a Formal Email in English
- ↑ Back to pillar: English Writing (Pillar)
Frequently Asked Questions
What is the main difference between informal and formal letters?
Informal letters are personal, warm, and conversational — written to people you know. They use contractions, casual language, and flexible structure. Formal letters are professional and respectful — written to strangers or people in authority. They avoid contractions, use proper grammar throughout, and follow a strict format with address, date, and clear sections.
Should I always write out the full address in a formal letter?
Yes. A formal letter should always include your full address at the top, the date, and the recipient’s address. This signals professionalism and is part of the expected format for business correspondence. Informal letters don’t require an address.
Can I use contractions in a formal letter?
No. In formal letters, avoid all contractions. Write “I am” instead of “I’m,” “do not” instead of “don’t,” and “you have” instead of “you’ve.” This is a key marker of formal register in English letter writing.
What should I do if I don’t know the recipient’s name in a formal letter?
Use “To Whom It May Concern,” or “Dear Sir or Madam,” at the start. However, if possible, research the name (check the company website, call ahead, ask). Addressing someone by name shows effort and professionalism. If truly impossible to find a name, the generic greetings above are acceptable.
How long should a formal letter be?
Formal letters should be concise — typically one page (three to four paragraphs). Every sentence should have a purpose. Avoid repeating yourself or adding unnecessary information. The shorter your formal letter, the more likely it will be read carefully.
Is email considered a formal or informal letter?
Email can be either, depending on the recipient and context. An email to a new client or your boss’s boss should follow formal letter rules (full greeting, no contractions, professional tone). An email to a colleague you work with daily can be informal and casual. The medium doesn’t determine register — the relationship does.
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