credit insurer asks for data about our customers and debtors

Debtor concentration is a risk indicator, not an accounting control

The credit insurer wants to know how dependent your business is on a small number of major customers. If 60% of your turnover comes from two clients, your business will collapse financially as soon as one of those two fails to pay or goes bankrupt. This is precisely the risk that a credit insurer covers, and therefore exactly what they want to see before assigning a limit to your own debtors or assessing you as a supplier. The question is not about your administration, but about concentration: how much turnover, with how many customers, in which sectors and countries.

Specifically, the insurer usually asks for the top-5 or top-10 customers with their share of turnover, the distribution across sectors and geographies, and sometimes the payment behaviour towards your own suppliers as an indication of your own liquidity buffer. You do not always have to share the names of individual clients; often an anonymised breakdown by turnover class or sector is sufficient. If you do not have that breakdown at hand, then "to be determined" is a more honest answer than an estimate you cannot substantiate — the insurer will then follow up specifically, and that is more efficient than correcting an incorrect figure.

Where this comes from: client due diligence and risk assessment

Credit insurers are themselves financial institutions and are subject to similar client due diligence obligations as banks, governed by the Act on the Prevention of Money Laundering and Financing of Terrorism. This explains why, in addition to the debtor question, it is often asked who the ultimate beneficial owners of your business are and what the origin of the capital is — the same law that requires client due diligence also requires an ongoing risk assessment of the relationship, and debtor concentration is a commercial, not a legally required part of this. The basic information about your business itself, such as registered address and directors, is already recorded under the Trade Register Act 2007 and is usually not requested separately.