why does the bank ask if I am connected to other customers

Relationship with other account holders is a customer due diligence question

The bank asks this to determine whether your enterprise is connected to other account holders at that same bank through shareholders, directors or family ties. This is not curiosity, but part of the mandatory customer due diligence that every bank must perform. The bank must have a complete picture of the group of entities and persons surrounding an account, among other things to be able to identify unusual money flows between connected parties. This often links to the question of the ultimate beneficial owners of the company: who the UBOs are, as this often also determines which other accounts are considered "connected".

In practice, this concerns three types of relationships: shareholding (parent, subsidiary or sister companies), management overlap (the same director at multiple clients of the bank) and family relationships in smaller enterprises. If you do not have this at hand, the usual answer is a reference to the UBO structure and the list of directors from the business register, supplemented with "no other relationships known" if that is the case. Note: this is a different question from at which banks the enterprise maintains accounts — that question concerns the enterprise's own banking relationships, not connection with other clients of that same bank.

Where this stems from: the AMLFT Act and the business register

The obligation to conduct this investigation is set out in the Anti-Money Laundering and Counter-Terrorist Financing Act, in the section on customer due diligence: banks must have insight into the control structure and the relationships of their clients in order to be able to identify unusual transactions. The information on directors and shareholders that the bank uses for this comes partly from the mandatory registration in the business register under the Business Register Act 2007. This platform does not provide a score or assessment of whether a relationship found is "suspicious" — that is up to the bank.