hTTi

OK, this is an old chestnut, but having read everything the search showed up on here, maybe this topic hasn't been directly asked on this new forum.

A chap an hour and a half down the road who is an employee here in Germany and also a veteran (UK) started getting his mil pension in April and the GKK (AOK) want him to back pay 20% - ish of this pension and then continue to pay this.

I think that's nonsense, He pays Beiträge as an employee - the usual 7,5% or whatever, the employer paying the other bit, and also presumably Pflege.
His other worldwide income only becomes of interest to the GKK if he becomes a Freiwillige member for whatever reason (eg. retires early)

They are being very insistent about this. Assuming I am right (quite possibly I am not) then what can he present to get out of this situation?

You're not right, please see here: https://www.tk.de/techniker/versicherun ... ge-2007446

Thank you for that.

Gosh. Ours specifically said, get a job, it'll be cheaper for you because we'll only take Beiträge from the wage, which is what we then did for a year.

In that case, tell him to change to your Krankenkasse

Yup, said that straight away