Confirm, in writing and from the institution's own pages, that the specific test is accepted for the specific thing you are applying for. Do that before comparing formats, before booking anything, and before reading a single opinion about which exam is easier.
The reason this is worth its own page rather than a line of advice is that the checking has a procedure, and skipping any step of it produces the same outcome: a valid score that cannot be used, which costs a term rather than a fee.
Eight questions to settle before booking
- ask the institution what it accepts. This single question removes most of the decision and is asked far too late by most candidates.
- check the minimum per paper. Many requirements specify both an overall score and a floor in each skill, and the floor is what catches people.
- check how long the score is valid. Two years is standard, and the Cambridge certificates are the exception.
- decide about a human examiner. If speaking to a person helps you, that rules some formats in and others out.
- check the result turnaround against your deadline, working backwards from the application date rather than forwards from today.
- compare the total cost, including travel to a centre and the likelihood of a resit.
- sit a full mock first, timed, in one sitting. It is the only way to know whether the format or the language is the problem.
- the cheapest test you cannot use is expensive, which is the whole argument for the first item on this list.
Four things to establish, and they are separate questions
Whether the test is accepted at all. What the overall requirement is. What the minimum for each component is, since almost every institution publishes both and most candidates read only the first. And whether the score is still valid on the date they will assess it, which is measured from the day you sat the test rather than from the day the result arrived.
That last one catches people who plan backwards from a deadline. A score with two years of validity sat in September is not usable for an assessment the following autumn if the institution's cut-off falls a fortnight the wrong side of it.
There is a fifth condition that applies to some routes and to no others: whether the test has to be taken at an approved centre. Where that condition exists it rules out at-home testing entirely, regardless of the score, and it is written somewhere other than the score requirements.
Where it stops: asking somebody who did it last year
The stall is treating this as a question with a known answer. It is asked on a forum, somebody replies confidently, and the reply describes what was true for their application, under the rules of that year, for a route that may not be yours.
Requirements change without announcement, and they change in both directions: tests get added to lists and removed from them, and minimums move. A confident answer from eighteen months ago is not out of date in a way anybody can see, because nothing in the reply says when it was written or what it applied to.
The only source that settles it is the institution, on its own domain, on a page you can date. Everything else is a hypothesis.
Dating the page you relied on
The Wayback Machine is free, needs no account, and does two jobs here that nothing else does. It shows when a requirements page last changed, which tells you whether the version you are reading is settled or was rewritten a month ago. And it gives you a permanent, timestamped copy of what the page said on the day you made your decision.
It replaced taking a screenshot and hoping you would still have it in eleven months, which is the usual precaution and which fails at exactly the moment it is needed, because the screenshot is on a phone that was replaced.
Its limitation is coverage: not every page is captured, and pages behind a login are not captured at all. Where it has nothing, save the page yourself as a file with the date in its name, which is the manual version of the same idea.
What it looks like when it goes wrong
The recognisable failure is an overall score comfortably above the requirement with one component under its published minimum. The application is refused on that component, the candidate re-sits the whole test, and the second attempt is prepared the same way as the first.
The second is the split acceptance: the department accepts the test and the immigration route does not, or the university accepts it for admission and a funding body does not. Both are true at once, both are documented on different sites, and nothing brings the two together except somebody checking both.
The third is a search result that is a cached older version of a real page. It is on the right domain, it looks official, and it is describing last year's rules.
Once the list is settled and more than one test survives it, the choice between them is made on how you perform rather than on reputation, which is what each test scores, and how to prepare for yours. The two that reward the most different rehearsals are computer scored, and what that changes about preparing and the four papers, the band scores, and what examiners reward.
What is left after that is a question about time rather than about the tests. Every score on this page has an expiry except one family of qualifications, and if the reason for sitting anything is several years out, that difference outweighs everything else here: B2 First, C1 Advanced, and the certificates that never expire.