Scoring reference: official IELTS Writing descriptors and assessment criteria. The examples here illustrate writing choices; they are not independently assessed complete scripts.
Vocabulary is only one part of Writing assessment. Grammar matters too: your response needs varied structures and control of grammar and punctuation. Start with errors that recur in your own answers. The six examples below show patterns to check, not a diagnosis of every writer at a particular band.
Grammatical Range and Accuracy: variety and control
Grammatical Range and Accuracy is one criterion covering both sentence variety and control. Range means you use a mix of simple and complex structures. Accuracy concerns your control of grammar and punctuation across the response. 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
Article use is worth checking in your own writing, especially in repeated noun phrases. 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.Illustrative original — article errors
The government should invest in education and healthcare.Illustrative rewrite — articles removed
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.Illustrative original — agreement error
The number of private cars has increased sharply over the last decade.Illustrative rewrite — agreement fixed
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.Illustrative original — preposition errors
Many people are addicted to social media and depend on their phones for information.Illustrative rewrite — prepositions fixed
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.Illustrative original — run-on
Public transport reduces congestion, and it is also cheaper than driving.Illustrative rewrite — one conjunction added
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.Illustrative original — tense shift
In many cities, air pollution is a serious problem because factories release toxic chemicals into the atmosphere.Illustrative rewrite — consistent present tense
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. Attempting a complex structure does not compensate for losing clarity or control. 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.Illustrative original — collapsed sentence
Although many governments have introduced policies to reduce carbon emissions, progress is slow because economic interests are often prioritised over environmental concerns.Illustrative rewrite — controlled complex sentence
The original piles up clauses and uses 'although... but' incorrectly. The rewrite keeps a clear main clause and removes the error. These examples demonstrate a correction rather than a whole-response band increase. Our linking words guide explains how connectors can make relationships clearer.
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.
Ten quick items, each hiding one of these errors. Train your eye to catch the patterns automatically.
Try the free error hunt drillIf 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. Review the suggested corrections against your writing and look for recurring patterns across several responses. AI feedback can miss errors or suggest an unsuitable change.