Short answer: The IELTS grammar mistakes examiners see most are article errors, tense drift, subject-verb agreement, wrong prepositions, run-on sentences and fragments, and word-form slips.
None is exotic, and each is rule-based, so fixing them is the fastest route from Band 6.5 to Band 7 - the accuracy half of Grammatical Range and Accuracy, a quarter of your band.
Band 7 in IELTS Writing does not require rare grammar - it requires "frequent error-free sentences." That means the fastest way up is usually not learning new structures but eliminating the small, repeated errors you already make.
This roundup gathers the mistakes examiners flag most often, shows a correct version of each, and points to the focused guides that fix them. Treat it as a checklist to run over your own writing.
The errors examiners see most
Grammatical Range and Accuracy is 25% of your Writing band and 25% of your Speaking band, and most lost accuracy marks come from a short, predictable list rather than from ambitious grammar gone wrong.
The Band 6 descriptor allows "some errors" that "rarely reduce communication," while Band 7 expects those errors to become occasional - see the full progression in the official IELTS band descriptors and how they combine in how IELTS Writing is scored.
The table below is that short list: the error type, a correct example, and the version that leaks marks.
The point of a roundup like this is triage. You do not make all seven errors equally; almost nobody does.
One or two of them account for most of your lost accuracy marks, and the quickest improvement comes from identifying which and attacking those, rather than worrying about the whole list at once.
Read each section below and be honest about which describes you - that is the error to drill first.
| Error type / rule | Correct example | Common error |
|---|---|---|
| Articles (a / an / the / zero) | The education system is failing. | Education system is failing. (missing "the") |
| Tense consistency | Social media affects sleep. | Social media affected sleep, and teenagers use it more. (unmotivated shift) |
| Subject-verb agreement | The number of users has grown. | The number of users have grown. |
| Prepositions | an increase in prices | an increase of prices |
| Run-on / comma splice | Costs rose, so profits fell. | Costs rose, profits fell. |
| Word form | a significant increase | a significantly increase |
Articles, tense, agreement, prepositions
Articles are the most frequent slip of all.
Use a/an for a singular countable noun mentioned for the first time, the when the noun is specific or already known, and no article for plural or uncountable nouns used generally: Education is important (general) but the education system in my country (specific).
Ask of each noun whether it is general or specific and most article errors disappear.
Articles reward one more habit: distinguishing general from specific across a whole paragraph.
The first mention of a countable idea often takes a - a solution has emerged - and every mention after that takes the, because it is now known: the solution works because... Uncountable and plural nouns used in a general sense take no article at all - governments should fund education - which is where speakers of article-free languages most often over-correct by inserting the everywhere.
When in doubt, decide whether you mean the thing in general or a specific instance of it, and let that choose the article.
Tense consistency is the next. Choose a tense and stay in it unless the timeline genuinely changes: describe general truths in the present (tourism creates jobs), narrate finished events in the past, and only shift when meaning requires it.
Drifting from present to past mid-paragraph for no reason is a classic Band 6 marker.
Subject-verb agreement breaks most often across long subjects, where the verb latches onto the nearest noun instead of the real one: The list of demands is long, not are. It has enough traps to deserve its own guide - see IELTS subject-verb agreement.
Prepositions rarely translate from your first language, so learn them inside the phrase - an increase in, depend on, result in, an impact on, concerned about - and drill the ones you get wrong rather than hunting for rules that barely exist.
Prepositions after common IELTS verbs and nouns are worth a memorised list, because they are unpredictable and high-frequency: lead to a result, a rise in numbers, responsible for a problem, benefit from a policy, a lack of resources, access to services.
Getting these fixed phrases right is one of the quiet markers that separates a Band 7 answer from a Band 6 one, because a wrong preposition never blocks meaning but always reads as an error.
Run-ons and fragments
These two punctuation errors do more damage to your accuracy score than their size suggests, because they make the examiner stumble.
A run-on (or fused sentence) jams two independent clauses together with no punctuation: Costs rose profits fell. A comma splice joins them with only a comma: Costs rose, profits fell. Both are fixed the same three ways - use a full stop (Costs rose. Profits fell.), a coordinating conjunction with a comma (Costs rose, so profits fell.), or subordination (As costs rose, profits fell.).
The reason these hurt more than their size suggests is that punctuation is part of Grammatical Range and Accuracy, not a separate concern.
A comma splice is scored as a grammar error, not a stylistic quibble, and because most candidates write several sentences of the same shape, the same splice tends to repeat - turning one habit into several logged errors.
The good news is that fixing the habit fixes all of them at once: learn to feel where one independent clause ends and the next begins, and you close the leak everywhere.
A fragment is the opposite problem: a piece punctuated as a sentence that cannot stand alone, usually a stranded subordinate clause - Although costs rose. - or a phrase with no main verb.
The cure is to attach it to the clause it belongs with: Although costs rose, profits held steady. If you tend to write very long sentences to show range, these errors are where that ambition backfires; the fix is to master subordination properly, which our guide to complex sentences for Band 7 covers in full.
Fragments most often appear when a candidate starts a sentence with a linking word and then stops, treating the linker as if it completed the thought - For example, the rise in fees. Which affected many students. Both pieces are fragments: the first has no verb, the second is a stranded relative clause.
Joined properly, they become one accurate sentence: For example, the rise in fees affected many students. If a "sentence" you have written cannot stand alone when read in isolation, it is a fragment.
Word form errors
A word-form error uses the wrong part of speech from the right word family - an adjective where a noun belongs, or an adverb where an adjective belongs.
Common examples: a significant increase (adjective + noun), not a significantly increase; economic growth (adjective), not economy growth; the government should analyse the data (verb), not should analysis the data.
The meaning is usually clear, but the slip is a visible accuracy error and often a lexical one too, so it can pull down two criteria at once.
These errors cluster around the academic words candidates reach for to lift their band, which is the irony: the attempt to sound advanced introduces the mistake.
The fix is to learn each academic word with its whole family - economy, economic, economical, economically - and the collocations it lives in, rather than memorising it as a single form.
A little-and-often vocabulary habit with the Word Coach builds exactly that, and the broader grammar for Band 7 guide shows where word choice and grammar meet.
Two word-form confusions are worth singling out because they are so common. The first is adjective versus adverb: use an adjective to describe a noun (a rapid increase) and an adverb to describe a verb (prices rose rapidly).
The second is noun versus verb from the same root, where the spelling barely changes - advice (noun) and advise (verb), effect (usually a noun) and affect (usually a verb), practice and practise in British spelling.
Because IELTS accepts both British and American spelling, be consistent with whichever system you choose, but never mix the noun and verb forms.
A before/after example
The paragraph below was written for this article as a teaching example - not a real test answer - to pack several of these errors into a few lines. See how many you can name before the rewrite.
Before: Nowadays technology affect our life in many way. It made communication easier, people can talk to anyone, this is a big advantage. The economy growth also depend of technology.
After: Nowadays technology affects our lives in many ways. It has made communication easier, and people can talk to anyone - a significant advantage. Economic growth also depends on technology.
The fixes, in order: technology affects (agreement), our lives in many ways (plural forms), a tense held steady across the present-perfect and present, the comma splice (...anyone, this is...) rewritten with a dash and a noun phrase, economic growth (word form, not economy growth), and depends on (agreement plus the correct preposition, not depend of).
No sentence became longer or more advanced; the paragraph rose a band because the errors were removed. That is the whole lesson of this guide in miniature.
A fixing routine
You cannot fix six error types at once while also generating ideas under time pressure, so separate the jobs. Write first, without policing grammar.
Then, in the last few minutes, run one targeted pass per weakness - one read hunting only for verbs (agreement and tense), one for the front of every noun (articles), one for sentence boundaries (run-ons and fragments).
Isolating a single error type per pass catches far more than a vague "check for mistakes."
One more low-tech tool: read your draft slowly in your head, sentence by sentence. Your ear catches what your eye skips - a missing article, a verb that does not agree, a sentence that runs on without a break.
Fluent readers race past their own errors silently, so forcing yourself to "hear" each word restores the friction that makes a mistake noticeable.
Do not try to fix everything the week before the test, either. Pick your single most frequent error and give it a fortnight of focused attention - in every essay you write, you check only for that, until it stops appearing - then move to the next.
Trying to police six error types at once usually means you catch none of them well. Sequential, one-at-a-time attention feels slower but raises your accuracy far faster.
Between exams, the real gains come from feedback that names your specific pattern, because everyone's list is different. The IELTSbiz Writing Checker scores an essay against the four criteria and flags each grammar error in place, so you learn whether articles, agreement or punctuation is your recurring leak.
Pair it with the focused guides - complex sentences for structure and subject-verb agreement for the trickiest cases - and drill the one or two errors that keep reappearing until they stop.
Conclusion
The grammar that keeps most candidates below Band 7 is not missing knowledge but repeated small errors: articles, tense drift, agreement, prepositions, run-ons, fragments and word form. Each is rule-based and cheap to fix.
Run this checklist over your own writing, drill the one or two errors that turn out to be yours, and you convert ambitious-but-flawed sentences into the frequent error-free ones the Band 7 descriptor rewards.