You can say "expertise in" or "expertise on". Both are correct and generally interchangeable. However, the phrase "expertise in" is much more common.
You can say "expertise in" or "expertise on". Both are correct and interchangeable in most situations. However, the phrase "expertise in" is much more common.
The company has developed its own expertise in a range of areas.
His expertise on artificial intelligence will help our technology team.
Source: Google Books Ngram Viewer
Instead of "having an expertise on", you can say being an expert in/on to sound more natural.
Do you need an expert in digital marketing?
