Here's the thing: relative clauses separate Band 6 writers from Band 7+ writers faster than almost any other grammar point. Most students can use them. Fewer use them correctly and confidently. Even fewer know when to use which, that, or who without second-guessing themselves mid-sentence.
In the IELTS writing and speaking assessment criteria, grammatical range and accuracy accounts for 25% of your overall band score. That's not trivial. A single relative clause error won't tank you, but consistent errors with these structures will absolutely cap your grammar score at Band 6. You'll plateau.
This guide shows you exactly what examiners expect at Band 7+, the mistakes that cost you points, and drills you can start today.
Band 6 relies on simple sentences. Band 7+ combines ideas efficiently. That's what relative clauses do: they let you link information without creating choppy, repetitive writing that sounds like you're learning English.
Check the actual IELTS band descriptors for Grammatical Range & Accuracy. At Band 6, you need "a variety of complex structures." At Band 7, you need to "use a variety of complex structures" and use them "accurately and appropriately." See the shift? Band 7 doesn't just want variety. It wants accuracy and appropriateness.
Why does this matter? Because relative clauses are the easiest complex structure to control. Passive voice requires subject knowledge. Conditionals demand careful tense control. But relative clauses? You just need to know the rules and apply them consistently.
This is where most students mess up. They don't distinguish between these two types, so they use wrong punctuation and the wrong pronoun.
Defining relative clauses give essential information. They identify which noun you're talking about. No commas. Remove the clause and the sentence loses its meaning.
Example: "The candidate who scored 8.5 in Reading won the scholarship." Without the relative clause, "The candidate won the scholarship" is vague. Which candidate? You need that clause.
Non-defining relative clauses add extra information. They describe a noun that's already identified. Use commas. Remove the clause and the sentence still makes complete sense.
Example: "Sarah, who scored 8.5 in Reading, won the scholarship." We already know who Sarah is. The clause just adds context. Remove it and you get "Sarah won the scholarship." Still works perfectly.
Why this matters on test day: many candidates write defining clauses with commas (wrong) or non-defining clauses without commas (also wrong). Both mistakes hit you under Grammatical Range & Accuracy. You lose band points for careless errors, even if you understand the rule.
You've heard this: use "that" for defining clauses and "which" for non-defining clauses. Sounds simple. But is it the whole story?
In British English (the standard for IELTS), both "that" and "which" can appear in defining relative clauses. "Which" in a non-defining clause is required. Here's what actually matters for your band score:
This distinction affects your score because mixing them awkwardly signals sloppy editing. Look at how it goes wrong:
Weak: "The report that we submitted last week, which was 15 pages long, revealed concerning trends." This mixes defining and non-defining awkwardly in one sentence. It's cluttered.
Better approach: separate them.
Better: "The report that we submitted last week revealed concerning trends. The document, which was 15 pages long, provided detailed analysis." Clean separation. Each clause does one job.
Or tighten it into one tight sentence:
Best: "The 15-page report that we submitted last week revealed concerning trends." One sentence. Zero ambiguity. Band 7 material.
Most Band 7 candidates nail "who" and "whose." They stumble on "whom." Here's the actual rule and how to use it without sounding robotic.
Use "who" when it's the subject of the relative clause. Use "whom" when it's the object. Simple rule. The problem: "whom" sounds overly formal to modern ears, so people avoid it.
Wrong: "The researcher who the university hired last year published three papers." "Who" is the object here, not the subject. Grammatically incorrect.
Right: "The researcher whom the university hired last year published three papers." Technically correct, but sounds stiff. Alternative: "The researcher that the university hired last year published three papers." Clearer, more natural.
"Whose" shows possession. It works for both people and things now.
Right: "The student whose essay won first place studied for six months." Or: "The organization whose mission is environmental protection received government funding." Both sound natural.
Speaking vs. Writing: In IELTS speaking, examiners won't penalize you heavily for using "who" instead of "whom." Native speakers increasingly drop "whom" in conversation. But in your writing, use "whom" correctly if it applies. It shows grammatical control at Band 7+.
This is where candidates plateau at Band 6. They stick to "who," "which," and "that." Band 7+ candidates sprinkle in relative adverbs: where, when, why. It's a small shift that signals sophistication.
Where replaces "in which," "at which," or "on which."
Right: "The office where she worked for ten years was recently renovated." More natural than "The office in which she worked..." Sounds like actual English.
When replaces "at which," "during which," or "in which."
Right: "The period when interest rates were lowest saw increased investment." Better than "The period during which interest rates were lowest..." Sharper and cleaner.
Why is rare but shows control. It replaces "for which."
Right: "The reason why the policy failed is complex." Though "that the policy failed" also works here.
Using these adverbs correctly signals Band 7+ control. But overusing them backfires. Stick to them when they genuinely clarify, not when they feel forced.
Let's walk through the mistakes real IELTS candidates make.
Error 1: Repeating the subject with a relative clause.
Wrong: "The technology that the company developed, it was revolutionary." You're naming the subject twice. Choose one structure.
Right: "The technology that the company developed was revolutionary." One subject. Clear.
Error 2: Leaving out the relative pronoun when you need it.
Wrong in formal writing: "The research we conducted last summer focused on climate change." In academic writing, examiners expect the pronoun.
Right: "The research that we conducted last summer focused on climate change." The pronoun signals formal, controlled writing.
Why it matters: In conversation, you can drop the pronoun: "The research we conducted..." But in IELTS writing, especially at Band 7+, include it. Examiners expect formal academic style, and the pronoun reinforces that.
Error 3: Wrong punctuation on non-defining clauses.
Wrong: "The CEO which founded the company in 1995 was recently awarded a prize." No commas around a non-defining clause, and "which" is wrong for people.
Right: "The CEO, who founded the company in 1995, was recently awarded a prize." Commas mark the non-defining clause. "Who" applies to people.
Let's ground this in actual IELTS tasks. Take a General Training prompt: "Write about a skill you've learned recently."
A Band 6 response reads like this:
"I learned photography. I took an online course. The course was helpful. I now understand lighting and composition."
Choppy. Repetitive. Each sentence does one small job.
A Band 7+ response builds complexity:
"The online photography course that I completed last year taught me techniques which I now apply daily. The instructor, who had 20 years of professional experience, explained how lighting and composition fundamentally shape visual storytelling."
What changed? Information got layered. One idea became three interconnected clauses. You showed:
For IELTS Task 2, stakes are higher. A typical prompt: "Some people say technology has improved life. Others say it's made life more complicated. Discuss both views."
Band 7+ candidates use relative clauses to present nuanced arguments without sounding forced:
"The devices that we use daily have undeniably enhanced productivity. However, the constant connectivity that these tools provide has created new forms of anxiety, particularly among users whose professional boundaries have blurred with personal life."
This structure is efficient. No word waste. No repetition. That's Band 7+ writing. When you combine relative clauses with academic linking words, you create sophisticated paragraphs that examiners respect.
Most candidates drill endlessly without improving. Here's a focused one-week plan that actually works.
Days 1-2: Identify relative clauses in real texts. Take 5 academic articles from your IELTS reading practice. Highlight every relative clause. Label each one: defining or non-defining. Note which pronoun and why. Spend 15 minutes max. The goal: train your eye to spot patterns.
Days 3-4: Rewrite weak sentences. Grab Band 6 essay samples from IELTS practice sites. Pick 8 sentences with choppy, repetitive structures. Rewrite each using relative clauses to reduce wordiness. Compare your version to the Band 8 sample. What did you miss? Did you punctuate non-defining clauses correctly? Did you vary your pronouns?
Day 5: Write a full essay (250 words minimum). Pick an IELTS prompt and write. Aim for 3-5 relative clauses naturally placed. Submit to our essay grading tool. Ask specifically about relative clause usage. Are your defining and non-defining clauses punctuated correctly? Did you use variety?
Days 6-7: Record yourself speaking. Answer two IELTS speaking questions. Use at least two relative clauses per answer. Play back and check: Are you pausing appropriately around non-defining clauses? Is your pronunciation clear? Did the clauses sound natural or forced?
One week of focused practice beats three weeks of aimless drilling. Quality always wins over quantity.
No. In standard British English, "that" cannot introduce non-defining clauses. Use "which" for things and "who/whom/whose" for people. If you use "that" in a non-defining clause, it's a grammatical error and examiners catch it immediately. This mistake alone can prevent you from reaching Band 7.
Don't. In formal academic writing for Task 1 and Task 2, examiners expect you to include the relative pronoun. Dropping it makes your writing sound conversational and loses marks for grammatical precision. The rule: include the pronoun in writing, even if it feels redundant.
Aim for 3-5 well-placed relative clauses in a 250-word essay. That's roughly 1-2 per paragraph. More than that starts to feel overdone and self-conscious. Quality beats quantity. Each relative clause should clarify or add meaningful information, not pad your word count.
Not necessarily. Relative adverbs are a bonus for range, but they're optional. You can reach Band 7+ using only "who," "which," "that," and "whose" if you use them accurately and appropriately. Relative adverbs matter when they fit naturally, not when you force them to seem advanced.
Defining clauses identify which noun you mean, so removing them changes the meaning. Example: "Students who scored above 7.5 passed" specifies only high-scorers. Non-defining clauses add optional detail about a noun that's already clear. Example: "My friend, who scored 7.5, passed" tells you extra information about a friend you already know. The key test: can you remove it? If the sentence still makes sense, it's non-defining.
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