Recently moved from B to C permit. Looking through the Tax forms I see I need to declare property abroad. (2 small investment flats i rent out but don't make any profit)

If I now declare this can I be fined (backdated) for not declaring it in the past 5 years of Quellensteuer?

Did you fill tax returns in the past 5 years in Switzerland ?

I would consult a (Swiss) tax agent to get it sorted out...

No i just paid the Quellensteuer and didn't fill in any tax forms in the past 5 years.
I don't make any income/ profit so didn't think i would need to...

Best to talk to your accountant.

You have income on the apartments and they have a value you haven't declared on your global wealth declaration in the tax return. Actually they would have been needed to be declared previously before. Best advice is to volunteer and inform them that you didnt understand before.

If they discover the situation they will take a different interpretation then if you volunteer the details and apologise for previous oversight.

No guarantees but dont hide the truth

Yes but in Switzerland we have capital taxes as well as income tax

Yeah I realise that now. I just received a provisorische form to fill in and hence have for the first time been reading about tax in Switerland.
I'm happy to declare the properties now but am just worried i'm going to be fined for not filling in any other form in the past years!

I don't think you will be fined, the tax liability on capital will be tiny. They almost certainly won't back date it either as you are allowed 1/3% of your capital as management expenses, the refund your due would exceed your liability in many cantons especially Zurich where capital taxes max out at about 1/3%

As your earnings were below 120k I am not sure you even had the option of a tax return.

Ok thanks That's the kind of answer i was hoping for! You're right, i'm earning under 120,000 chf and was never asked to fill in a tax form.
Just had a sudden panic that I should have been declaring my "wealth"

Guess it's time for me to start learning about finance