Grammar is one of the four criteria in IELTS Writing and a significant factor in Speaking assessment. Most IELTS grammar mistakes are systematic — they appear repeatedly across an individual's writing because they reflect gaps in specific grammatical structures. Identifying your systematic errors and correcting them produces rapid, measurable improvement. This guide covers the most common IELTS grammar mistakes.
1Subject-Verb Agreement Errors
Subject-verb agreement errors are extremely common in IELTS Writing and occur most frequently when the subject and verb are separated by intervening phrases. Example error: 'The number of students who study abroad have increased significantly.' Correct: 'The number of students who study abroad has increased.' (The subject is 'The number', singular, not 'students'.) Pattern: 'The number of [plural noun] + singular verb.' Compare: 'A number of students have enrolled' — here, 'A number of' acts as a quantifier meaning 'several', so plural verb is correct. Fix: whenever there is a noun phrase between subject and verb, identify the grammatical subject (ignore intervening phrases) and ensure verb agreement matches that subject.
2Article Errors (A/An/The)
Article errors are among the most persistent grammar mistakes for speakers of languages without articles (many Asian and Eastern European languages). The rules: 'The' — specific or previously mentioned item. 'A/An' — first mention, one of many. No article — uncountable nouns in general statements. Common IELTS errors: 'The government should reduce the pollution' (pollution here is a general concept, not specific — should be 'reduce pollution'). 'Education is important for the society' — 'society' in a general sense takes no article. Fix: when you use 'the', ask yourself: 'Is this noun specific and identifiable to my reader?' If the answer is no, consider whether 'a/an' or no article is correct.
3Relative Clause Errors
Relative clauses are essential for Band 7 grammatical range, but errors in them are common. The most frequent errors: incorrect use of 'which' vs 'who' (use 'who' for people, 'which' for things), missing commas in non-defining relative clauses, and omitting the relative pronoun when it cannot be omitted. Example error: 'The researchers which conducted the study found that…' Correct: 'The researchers who conducted the study found that…' Non-defining relative clause (with commas): 'Climate change, which has accelerated in recent decades, poses existential risks.' Defining relative clause (no commas): 'The approach that produces the best results is…' Fix: whenever you write a relative clause, verify: (1) who vs which, (2) defining (no commas) vs non-defining (commas), (3) correct placement immediately after the noun it modifies.
4Tense Consistency Errors
Tense consistency errors — switching between past and present tense within a paragraph without reason — are common in both Writing and Speaking. They reduce Grammatical Range and Accuracy scores significantly because they signal lack of control. Common patterns in Writing: Task 1 responses that mix past tense (appropriate for historical data: 'increased in 1990') with present tense inappropriately. Task 2 essays that begin in present tense and shift to past for examples without explanation. Fix: decide your primary tense before writing. Task 1: past tense for historical data (line graphs with historical dates), present tense for current/projected data. Task 2: primarily present tense for general statements, past tense for specific historical examples, future tense for predictions. Once decided, be consistent within each section.
🎯 Key Takeaway
Grammar improvement is systematic: identify your top 2–3 error types from this list, study the rule specifically, then complete 30–50 targeted exercises on that rule alone (not general grammar practice, but exercises specifically on that one error). This focused approach corrects systematic errors faster than broad grammar review.