Is it illegal ask for proof of existing of exiting our apartment?

Yes,  through the university where they have studied, they got resident permit for the duration of the course, with our address as primary address, based on rental contract. I understand commune will not respond to my question due to privacy laws so won't bother attempting to check it.

I will ask them to settle pending arrears, for the charges and for the damages.
Once it is done, will sign to have the bank guarantee released.

Thanks for the help.

The problem is that if your ex-tenants didn't de-register from the commune, if they would have any debt, the bailifts are allowed to penetrate in your apartment (their Worldwide Main Address) to take away all the furniture, appliances etc... for which you can't prove (via bills) that your are the owner!!

Hello,

I see 2 concerns:
1: getting the the money they own you back ( 60 euro+ damage)
> Just ask them to come for the bank. I would call the bank in advance to ask them the procedure if indeed you want to keep some of their warranty money. The best is to establish before hand a report of the damage and the charge amount. Send it to them for signature.  If you all agree it wil be very easy.
If you do not agree> negociate, the judicial way for this is complex, lenghty and not worthwile.  Just keep in mind it is their money and until you sign torelease it it is blocked , this is a powerfull leverage in negociation :-)

2: They registered in your appartment.
> the easy way, speak with the local policie agent ( the one dealing with your neighbourhood ).  I got the same issue in the past. I called, prooved I am the owner of the house and told them of my doubts about some ppeople using my address illegally.
I never asked for the names of people registered ( i did get them).  I listed them the people officially registered, asked them if my  list matched theirs, it did not they mentioned the names they had just for me to confirm they had been tenant at some time or not. (some name never actually lived at my place!!)
The second way, go to the commune administration with the contract cancellation proofs and tell them the same thing. Just present it that you bring them data so they can confirm to you there is no illegal situation ( again do not ask who ).  focus on what they can tell you : if everything is ok, nto on what they cannt tell you : who is registered there. (even though they might tell you as you proove ownership)

There were so many problems with banks when releasing deposits that now they require the physical presence of all the people who have signed to block the deposit. If one is missing, the bank will never accept to release the deposit. People are not obliged to go to the same agency, everybody can go to the nearest agency of  his new home in Belgium, but bank employees require to see the person signing the release. So physical presence is mandatory in one agency of the bank!