It depends. For British English, the answer is very simple : if you are using British English, you only use 'have got'. 'Gotten' is not used any more. The word 'gotten' disappeared hundreds of years ago everywhere in the world .... apart from in North America. In American English, the archaic past participle 'gotten' has remained in use. This means that 'gotten' is used in perfect constructions wherever 'get' is the main verb. For example, if you want to say "I've received an answer" using the verb 'get' in AmE, you will need to say "I've gotten an answer"; if you want to say "He's become old" using the verb 'get', you will need to say "He's gotten old". The only context where it is acceptable to say 'have got' or 'has got' in AmE is as in informal, idiomatic alternative to the present tense of 'have/has" where 'have/has' refers to possession of some kind - for example "I've got a problem". It's also widely used to express a need or obligation: for example "I've got to go" (further reduced to the non-standard "I got to go" or even "I gotta go"). So, just to recap: 1. Where 'get' is the main verb in a present perfect or past perfect sentence (meaning receive, obtain, become, achieve, enter and so on): BrE: Life has got easier. AmE: Life has gotten easier. 2. Where 'got' has no meaning, but is simply used to reinforce the verb 'have/has' in the present tense, for example to express an obligation: BrE and AmE: You've got to study. I hope that helps.