Writing Formal and Informal Letters: Controlling Register
Learn how to control tone, structure, and vocabulary to write convincing formal and informal letters, with attention to purpose and audience.
A letter is a text produced for a specific reader in mind, which makes it a perfect place to practise register control -- adjusting your tone, vocabulary, and structure to suit exactly who you're writing to and why. In this unit on empathy, letters give you a way to step into someone else's perspective and imagine how they would actually speak or write, rather than writing generically.
The biggest mistake at this level is treating formal and informal letters as the same letter with different greetings. They are not. A formal letter should sound like a stranger being persuasive and precise; an informal letter should sound like you, talking to someone you already know.
The level of formality, tone, and vocabulary a writer chooses based on their relationship to the reader and the purpose of the text. In letters, register shows up in greetings, sentence length, contractions, and word choice.
| Feature | Formal letter | Informal letter |
|---|---|---|
| Greeting | Dear Mr/Ms [Surname], or Dear Sir/Madam, | Hi [first name], or Dear [first name], |
| Sign-off | Yours faithfully / Yours sincerely | Love, / Take care, / See you soon, |
| Contractions | Avoided (do not, cannot) | Used naturally (don't, can't) |
| Sentence style | Longer, complex sentences; precise vocabulary | Shorter, varied sentences; conversational asides |
| Purpose language | States purpose directly and early | Purpose can unfold gradually, chattily |
| Tone | Respectful, measured, impersonal | Warm, personal, may include humour |
- Heading: your address (optional in informal letters), the date, and the recipient's address for formal letters
- Greeting: matched to register (Dear Sir/Madam vs Hi Sam)
- Opening line: state your reason for writing (formal) or open with a friendly connector like a question about the reader (informal)
- Body paragraphs: one idea per paragraph, building your explanation, request, or story logically
- Closing line: a clear final message -- a call to action (formal) or a warm sign-off line (informal)
- Sign-off and name: matched formality (Yours sincerely, Amrita Shah vs Love, Amrita)
A formal letter written with empathy: complaining about a closed community garden
- Heading and greeting: '14 Birch Lane... Dear Ms Okafor,' -- the formal address and surname greeting immediately signal that this is not a casual note; it is directed at someone in an official capacity.
- Opening line states purpose without delay: 'I am writing to express my concern about the planned closure of the Elmridge Community Garden.' Formal letters do not build up slowly to their point -- they name it in the first line.
- Body paragraph 1 gives context calmly: 'For the past three years, this garden has been the only outdoor space where elderly residents of Elmridge Court can walk safely and speak with neighbours.' Notice there are no contractions and the sentence is longer and more explanatory than casual speech would be.
- Body paragraph 2 shows empathy through specific, non-emotional language: 'Many residents have described the garden as the one place they do not feel isolated. Removing it risks removing that connection entirely.' The empathy is expressed through evidence and precise wording, not exclamation marks or slang.
- Closing line makes a clear, respectful request: 'I would therefore ask that the council reconsider this decision and consult residents before any final vote.' A formal letter's ending should tell the reader exactly what you want to happen next.
- Sign-off matches the greeting's formality: 'Yours sincerely, Daniel Osei' -- because the writer used the recipient's name (Ms Okafor), the correct sign-off is 'Yours sincerely', not 'Yours faithfully' (which is reserved for 'Dear Sir/Madam').
Yours sincerely vs Yours faithfully trips up almost everyone. Use Yours sincerely when you know the reader's name (Dear Mr Osei,). Use Yours faithfully when you don't (Dear Sir/Madam,). Getting this backwards is a small but noticeable slip in Criterion D (using language).
An informal letter uses the same underlying purpose -- to communicate something to a specific reader -- but everything about its voice changes. Imagine the same student, Daniel, writing to his cousin about the same garden closing:
Hi Amara,
You won't believe what's happening to the garden near my building -- they're shutting it down! Remember how we used to sit there after school? I'm actually pretty upset about it, not gonna lie. A bunch of us are writing letters to try to stop it. Anyway, how's your new school going? Tell me everything.
Miss you loads,
Daniel
Notice the contractions (won't, I'm, gonna), the direct address to shared memory, the casual aside ('not gonna lie'), and the sign-off that expresses feeling rather than formality. Both letters are honest and can both show empathy -- but the register is doing completely different work in each.
- Does my greeting match my register (Dear Sir/Madam vs Hi [name])?
- If formal, have I avoided contractions throughout?
- If informal, does my letter still sound like a real, specific person talking to another real, specific person?
- Does my opening line make my purpose clear early, especially in a formal letter?
- Does my sign-off match my greeting (Yours sincerely with a named recipient; Yours faithfully with Dear Sir/Madam)?
- Have I kept one clear idea per paragraph rather than jumping between topics?
- Register = the level of formality chosen to suit reader and purpose -- it must stay consistent throughout the letter.
- Formal letters: no contractions, precise vocabulary, purpose stated early, Yours sincerely (named reader) or Yours faithfully (Dear Sir/Madam).
- Informal letters: contractions welcome, conversational asides, personal sign-offs like Love or Take care.
- State your purpose directly in the opening line of a formal letter -- do not delay it.
- One idea per paragraph keeps both formal and informal letters organised (Criterion B).
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