The data are based on the one hand on regulated reports to the National Bank, both of an administrative nature and survey-based. The reporting to the national Bank of Belgium is executed via the tool OneGate. However, publicly available market information and information supplied by the market organisations is also used.

The credit institutions are an important direct data source. Credit institutions established in Belgium report to the NBB on their financial position on a territorial, corporate and consolidated basis via "Scheme A", as it is called. The reporting frequency varies according to the nature of the information. The following data are supplied:

• monthly: balance sheets and off-balance-sheet items and reports on such matters as cash balances and interbank claims, interbank liabilities, lending, the deposit basis and the securities held;
• quarterly: profit and loss accounts and additional information, including a detailed statement of the securities portfolio;
• annually: the treatment of the results.

The data on non-monetary financial institutions (non-monetary institutions for collective investment, listed companies, insurance companies, pension funds, etc.) are taken mainly from the body supervising those institutions or professional associations, such as the Belgian Association for Collective Investment Institutions.

In the financial institution sector, surveys are conducted on various financial products. This primarily concerns surveys on "dematerialised securities of the Belgian government debt and dematerialised treasury bills and certificates of credit". Another survey covers "applications for mortgage loans" and "mortgage loans executed" and is conducted jointly with the Credit Industry Association.