Is it okay to use informal contractions (like "gonna", "wanna", "gotta") in the IELTS Speaking test?

The answer is yes.

Some examiners say that the IELTS Speaking test should be formal and informal contractions should not be used. However, this is completely incorrect. The IELTS Speaking test is designed to assess naturalness in spoken language, not to evaluate one’s ability to present at a large conference, so there's no need to be overly formal.

The ultimate goal of this test is to assess how much you sound like a native speaker. And how many native speakers use phrases like "I want to," "I’m going to," or "I’ve got to" in everyday conversation?

That said, it’s important to realize that if someone uses these phrases in a very memorized way, it is possible that they might lose points. The difference between sounding memorized and natural, in my experience, is that I speak these phrases very quickly 😁 and don’t overuse them. So, if someone uses these phrases too slowly and overuses them, they should be careful.