Ag Nik, you have to and always should have put a tax return in even if you are non-resident!
I had a good accountant in Agios Nikolaos until he decided to ditch all of his ‘foreign’ clients because of the hassle and confusion with the ever changing rules for us non-residents. I now use one in Neapoli who seems pretty good and can give you the details if you wish.
I suggest that if you haven’t submitted a return (even when it is effectively a nil return) you need to do so pronto to alleviate any problems in the future.
Just To clarify….That is 50 euro for each missing tax return since you got your tax number plus the cost of filing each tax return. In my case our previous accountant missed two returns so we paid 200 euros extra to catch up. We were not living here at the time so assumed the accountant had taken care of these matters for which we had paid him. Needless to say we now have a different accountant.