"Have got" used with "since"

The use of have got with since in this sentence is incorrect for the following reasons:

• since denotes time duration from past to present, marked by since + fixed past time point. As such, the present perfect tense is appropriate. As in:

They've lived here since 1990

He's been here since the store opened

• verb phrases using since with the above meaning need to express duration (such as action verbs showing duration, e.g. live/rain/work/play or state verbs, e.g. be/like/love). The verb get in its original meaning expresses short, complete actions - and is synonymous in your example above with obtain, receive, both of which, as short action verbs, are incompatible with the use of since to show duration of state or action.

• the confusion arises from the evolution of the verb get into the phrasal expression have got, which essentially only has a (n.b.)present tense meaning of have / own / possess. As this refers to the present, it is grammatically incorrect to use as a present perfect with since (even if it looks like it is a present perfect with have+p.p). If you substitute the example with a synonym, it may help exemplify the error

I have obtained a bank account since I was 18 *

• The obvious correction would be to replace get with a verb showing possession over duration, for which the best choice in my opinion would be have, as in:

I have had a bank account since I was 18 (past to present)

and to finish off, you can state your possession of it now, but without the time expression.

And I have still got the bank account now.(present)