IELTS grammar: Formal vs. Informal Register

Register refers to how formal or informal a piece of language is, and it is judged separately from grammatical correctness — a sentence can be entirely free of grammar errors and still score poorly if its register doesn't match what the specific task requires. Academic Task 1 and Task 2 essays require consistently formal, academic register throughout; General Training Task 1 letters require a register that depends entirely on who the letter is addressed to, which is the detail most candidates never learn precisely; and Speaking occupies a register of its own, natural and conversational but not identical to either extreme. The error pattern worth naming upfront is not usually an isolated wrong word — it's registering drift, where a response starts in the correct register and gradually slides into the wrong one as the writer's attention shifts from register to content, which an examiner notices even when every individual sentence would pass in isolation.

General Training Letter tasks actually specify three distinct registers, not two, and treating them as a single "informal letter" category is itself a common error. An informal letter, to a friend or close family member, uses first names, contractions, casual vocabulary, and a warm, personal sign-off ("Love," "Take care," "Best, [name]"). A semi-formal letter, to someone you know professionally but not intimately — a landlord, a colleague, a neighbour — sits in between: fewer contractions, more measured vocabulary, but still personally addressed and not stiffly impersonal ("Dear Mr. Patel," ending with "Kind regards"). A formal letter, to someone you don't know personally — a company, an institution, a stranger in an official capacity — uses full forms throughout, no idioms, and a standard formal closing ("Dear Sir/Madam," ending with "Yours faithfully" if the recipient's name is unknown, or "Yours sincerely" if it is known). Misjudging which of the three a prompt calls for is a register error before a single sentence is even written.

Contractions are one of the clearest, most mechanical register signals available, and they map cleanly onto this three-tier system: fully used in informal letters ("I can't wait to see you," "it's been ages"), used sparingly if at all in semi-formal letters, and avoided entirely in formal letters and in Task 2/Academic Task 1, where the full form is expected throughout ("cannot," "it has been," "I would like to"). A single stray contraction in an otherwise formal Task 2 essay — "It's often argued that..." instead of "It is often argued that..." — is a minor slip in isolation, but several across an essay start to read as a genuine register lapse rather than an occasional oversight.

Vocabulary formality follows a similar but less mechanical pattern: phrasal verbs, idioms, and everyday vocabulary suit informal writing and Speaking, while their more formal, often Latinate equivalents suit Task 2 and Academic Task 1. "A lot of" becomes "a significant number of" or "a considerable proportion of"; "get better" becomes "improve"; "kids" becomes "children"; "find out" becomes "determine" or "establish"; "put up with" becomes "tolerate"; "a bit" becomes "somewhat" or "to some extent." This isn't a rule that phrasal verbs are always wrong — many phrasal verbs are entirely standard even in formal register ("carry out," "point out") — but a Task 2 essay saturated with conversational phrasal verbs and vague quantifiers reads as under-formal regardless of how grammatically correct each sentence is.