Question: Is British English or American English accepted in the ESOL tests?
In general the language input to the Trinity College London and Cambridge University ESOL tests is likely to be of a standard British English variety. Some American English terms are included in the vocabulary lists. The Listening test contains both British and American accents. In terms of a candidate’s output, both standard British English and standard American English are equally acceptable.
The most important rule of thumb is to be consistent in using either British or American spelling/ grammar/ vocabulary.
Here are a couple of grammar differences explained in the article, as well as activities and tips for you to enjoy!
Differences in American and British English grammar - article | Onestopenglish
British vs. American English - Activities and tips