Key takeaways
- 01Grammar counts for exactly 25% of your band, and the descriptor rewards range AND accuracy — not just safe, error-free sentences.
- 02The same six mistakes appear in almost every Band 6.5 script: articles, subject-verb agreement, prepositions, run-ons, tense shifts, and collapsed complex sentences.
- 03Fixing your single most frequent error is usually enough to lift Grammatical Range and Accuracy by half a band, which often rounds your overall score up.
Vocabulary gets all the attention. Candidates stuff their essays with 'moreover', memorise collocation lists, and hope a rare word here or there will impress the examiner. But while everyone is chasing lexis, grammar is quietly capping them at Band 6.5. It is worth exactly the same 25% of your score, and the Band 7 descriptor demands both range and accuracy, not just safe, simple sentences that happen to be error-free. Here are the six mistakes examiners see the most, and one change that fixes each.
Grammatical Range AND Accuracy — both halves count
The Grammatical Range and Accuracy descriptor is two criteria in one. Range means you use a mix of simple and complex structures. Accuracy means most of your sentences are error-free. Band 7 asks for 'a variety of complex structures' and 'frequent error-free sentences.' The key word is both: a script full of flawless short sentences caps your range, and an ambitious script full of broken complex sentences caps your accuracy. The six mistakes below are where the balance usually breaks. For the full picture of how the four criteria combine, our scoring guide breaks each one down.
1. Article errors — a, an, the, and zero article
Articles are the single most frequent grammar error in IELTS scripts, and they are especially visible because they sit at the front of noun phrases where the examiner cannot miss them. The full article system is complex, but two rules cover most mistakes: use 'the' only when the reader already knows which specific thing you mean, and drop the article entirely for general plurals and uncountable nouns.
The government should invest in the education and a healthcare.
The government should invest in education and healthcare.
The word 'the' before 'education' signals a specific system the reader has not been introduced to. 'A healthcare' fails because healthcare is uncountable. Dropping both articles fixes the sentence completely, and the correction costs you nothing in word count or complexity.
2. Subject-verb agreement slips
A plural subject with a singular verb, or the reverse, is one of the fastest ways to signal Band 6 grammar. The error is small, but it appears in almost every Band 6.5 script, and examiners are trained to spot it in the first few lines.
The number of private cars have increased sharply over the last decade.
The number of private cars has increased sharply over the last decade.
The subject is 'the number', which is singular, so the verb must be 'has', not 'have'. The trap is the word 'cars', which sits closer to the verb and feels plural. Ignore the noun inside the prepositional phrase and match the verb to the head noun. This same pattern causes errors with 'a group of people are/is', 'the list of items were/was', and 'one of the reasons that is/are'.
3. Preposition errors
Prepositions are small, frequent, and wrong just often enough to drag down your Lexical Resource score too, since many preposition errors read as collocation failures. The fix is not to memorise a list of rules but to learn prepositions attached to the words they belong with, as fixed chunks.
Many people are addicted with social media and depend in their phones for information.
Many people are addicted to social media and depend on their phones for information.
Three errors in one sentence: 'addicted with' should be 'addicted to', 'depend in' should be 'depend on', and the choice changes because each preposition belongs to its verb, not to a general rule. Learn 'addicted to' and 'depend on' as single units rather than separate words you assemble under pressure.
4. Run-on sentences and comma splices
A run-on joins two complete clauses with no punctuation or conjunction. A comma splice joins them with just a comma. Both are common in timed writing, where the hand moves faster than the planning, and both signal to the examiner that you do not control sentence boundaries.
Public transport reduces congestion it is also cheaper than driving.
Public transport reduces congestion, and it is also cheaper than driving.
One coordinating conjunction fixes it. Alternatives: a semicolon ('reduces congestion; it is also'), a subordinator ('Because public transport reduces congestion, it is also cheaper'), or two separate sentences. Use whichever keeps your paragraph rhythm natural. The rule is simply that two independent clauses need more than a comma between them.
5. Tense inconsistency
Switching tenses mid-paragraph without a reason confuses the reader and reads as a lack of control. The most frequent version is mixing present and past when describing a general, ongoing situation.
In many cities, air pollution is a serious problem because factories released toxic chemicals into the atmosphere.
In many cities, air pollution is a serious problem because factories release toxic chemicals into the atmosphere.
The sentence describes a current, ongoing situation, so both verbs need the present simple. Decide your time frame before you write each paragraph and check every verb against it. Our Task 2 structure guide covers the paragraphing that makes this easier to control.
6. Complex sentences that collapse
This is the mistake that traps ambitious writers. At Band 6.5, a candidate attempts a complex structure, loses control of the grammar halfway through, and the sentence becomes unreadable. The examiner does not reward the attempt; the error counts against accuracy. Band 7 writers use complex sentences they can finish cleanly, not the most complex sentence they can imagine.
Although many governments have introduced policies to reduce carbon emissions but the progress is slow because of economic interests which are often prioritised over environmental concerns by politicians who are elected on short-term platforms.
Although many governments have introduced policies to reduce carbon emissions, progress is slow because economic interests are often prioritised over environmental concerns.
The Band 6 version piles clause on clause until the reader loses the thread, and the 'although... but' structure is a direct grammatical error in English. The Band 7 version makes the same point in one controlled complex sentence with a clear main clause and a single layer of subordination. One clean complex sentence always beats three tangled ones, and the linking words guide explains how connectors fit into this without overloading it.
How to fix them in practice
Spotting these errors in your own writing is hard, because you read what you meant, not what you wrote. Here is what actually works, built around how our Band 7 guide recommends structuring your practice.
- Hunt one error at a time. Spend a week checking only for article errors in every essay you write. The next week, hunt only subject-verb agreement. Chunking it prevents overload, and by week six you will have addressed every pattern.
- Read your essay backwards, sentence by sentence, from the conclusion to the introduction. This stops your brain from auto-correcting and makes each sentence stand alone so errors surface.
- Keep a personal error log. Every time the grader or a tutor flags a grammar slip, write the incorrect sentence and the fix in a notebook or notes app. The errors you make are not random; you make the same five or six mistakes on repeat.
- Leave three minutes at the end of every timed essay to hunt your known errors. Do not try to fix everything. Scan only for the one or two patterns you know you are prone to. Three minutes of targeted proofreading is often the difference between a 6.5 and a 7.
If you are not sure which of the six mistakes is most frequent in your writing, paste an essay into the grader and check your Grammatical Range and Accuracy score. The sentence-level feedback highlights each error by category, so you can spot your pattern in a single submission and know exactly what to fix first.
Find out which grammar mistakes are capping your band.
Grade my essayFrequently asked questions
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Hannah Reed
Hannah writes the ieltsprep Writing guides from the four official band descriptors and thousands of marked essays, focused on what actually moves a band, not exam-mill templates.
Written from the official public band descriptors