Quick answer: your OET letter is scored on six named criteria. Purpose carries up to 3 marks, and Content, Conciseness & Clarity, Genre & Style, Organisation & Layout and Language carry up to 7 each. An assessor scores every criterion separately against a published level descriptor, and the six scores are combined and converted to the 0 to 500 scale, where 350 is the grade B line most regulators want. OET names the grade B target outright: 2 out of 3 for Purpose and 5 out of 7 on the other five. Each criterion, its killer mistake and its fix are below.
Here is the sentence that changes how you write forever. Your letter is not marked on vibes. It is marked on six named criteria, by a trained assessor, with a published level descriptor for each.
And here is the tragedy I watch every week. Students write forty practice letters without ever reading the six things those letters are judged on. That is playing a sport for a year without learning how points are scored. Read this page once, slowly, and every letter you write afterwards will be aimed instead of hoped.
The six criteria and their marks
| Criterion | Marks | The one line meaning |
|---|---|---|
| Purpose | up to 3 | Is the reason for the letter immediately clear, early? |
| Content | up to 7 | Did you select the right case notes for this reader, and report them accurately? |
| Conciseness & Clarity | up to 7 | Did you leave out what this reader does not need? |
| Genre & Style | up to 7 | Does it read like a clinician’s letter: formal, factual, right register? |
| Organisation & Layout | up to 7 | Does information arrive in the order the reader needs, in clean paragraphs? |
| Language | up to 7 | Grammar, vocabulary, spelling, punctuation, sentence control. |
Now notice what almost nobody notices. Purpose carries 3 marks. Everything else carries 7. And Language, the thing you worry about most, the thing you buy grammar books for, is one criterion out of six.
Look at what sits beside it. Content, Conciseness & Clarity and Organisation & Layout are all about the same three decisions: what you chose to include, what you cut, and the order you put it in. Those three carry 21 marks between them. Language carries 7. Your English is rarely the problem. Your decisions are.
Criterion by criterion: what the assessor wants, and the killer mistake
1. Purpose. The assessor should know why this letter exists within the first sentences, and the urgency should match the case. The killer mistake: burying the reason in paragraph three, or writing an opening that gives the name and the date and never the point. The fix is the Three Things Introduction. → The OET referral letter
2. Content. The case notes always contain more than the reader needs. This criterion pays you for choosing what this reader must know, completely and accurately, and it punishes invented details and copied irrelevance. The killer mistake: transferring everything, because leaving things out feels dangerous. Selection is a skill, and it is trainable on real cases. → Free case notes
3. Conciseness & Clarity. The twin of Content: what you correctly left out, and how cleanly you said what stayed. The killer mistake: the 260 word letter. The body belongs around 180 to 200 words, and every sentence past the reader’s need costs you here.
4. Genre & Style. A letter between professionals: formal, factual, no chatting, no drama, correct titles, appropriate opening and closing. The killer mistake: mixed register, a formal opening that collapses into spoken English by paragraph two. Starter Frames hold the register steady. → Sentence formation
5. Organisation & Layout. Information in the order the reader needs it, one idea family per paragraph, a shape the eye can follow. The killer mistake: copying the case notes’ order instead of the reader’s order. The fix is the Rearrangement Logic in the letter guide.
6. Language. Grammar, vocabulary, spelling, punctuation. Accurate beats ambitious: a clean simple sentence outscores a broken beautiful one. The killer mistake: showing off. The Connector Chain gives you controlled variety without the risk.
So what is the passing score?
OET answers this one directly, and the answer is the most useful sentence on this page. A candidate securing grade B has scored 2 out of 3 for Purpose and 5 out of 7 on each of the other five criteria. That is your target, written by the people who set the test. Not “write well”. Five out of seven, five times, and two out of three once.
The six scores are then combined and converted to the 0 to 500 scale, and 350, grade B, is the line most regulators want, with the UK’s NMC and several others accepting 300, a C+, in Writing. Check your own country’s line with every rule shown. → OET eligibility checker
One honest limit while you are here. OET publishes the criteria and their level descriptors, and it publishes that grade B benchmark, but it does not publish the arithmetic that turns six criterion scores into your 500 scale number, and it never says the six are weighted equally. So treat the marks above as what the rubric shows you, which is a great deal, and treat anyone selling you an exact formula with suspicion.
Now the uncomfortable question
You know the six criteria now. Can you see them in your own letter?
Almost certainly not, and that is not an insult, it is how eyes work. You cannot see your own repeating mistake, which is exactly why it repeats. The assessor reads your letter through six lenses you have never looked through. The fastest way to close that gap is to have a trained human mark your real letters through the same six, criterion named, the line to change shown, a projected score given. That is what the writing correction programme does. → Get your letters corrected
Before that, do the free half. Write one letter today under exam conditions, on real case notes. → Free OET writing case notes · The complete Writing guide
How this page stays accurate
The six criteria, their names and their marks were read on 7 September 2026 from OET’s own documents: the Writing sub-test: Assessment criteria and level descriptors PDF, its results and scoring page, and its writing guide, which states the ranges in so many words. Two things worth knowing if you go and check yourself. OET’s site is now oet.com, and the 2018 criteria PDF that half the internet still links to is a dead link. And the current PDF carries no version number and no printed date, which is why this page dates the day it was checked rather than the document. If OET revises the criteria, this page changes the same week.
About the author
Dr. Nasir Bukhari is the Executive Director of CliniVerba, the house behind OET HQ, and an officially trained OET teacher, certified in all four skills by OET’s Head of Education. He has sat the OET exam and cleared it, and has taught healthcare professionals in more than 40 countries. More about Dr. Nasir.