The securities system is a digital tool where information about Danish taxpayers' securities holdings, as well as purchases, sales, and dividends, is registered. The system is based on reports from banks and custodians, which are obligated to submit data to the Danish Tax Agency.

When information is reported, the Danish Tax Agency can automatically calculate gains and losses according to the realization principle or mark-to-market principle and transfer the results to the individual's tax information form. If information is missing, such as purchase date or acquisition cost, it is marked in the system, and the taxpayer can add it themselves.

The purpose is to ensure correct and consistent taxation of stock income and to ease the taxpayer's workload. By automating the calculation, the risk of errors is reduced, and the annual tax assessment can be pre-filled with relevant information, which the taxpayer must then verify.

You are not required to use the securities system; it is solely a support tool to ensure correct reporting of gains and losses. If the information is available in the system, the Danish Tax Agency will typically use it as the basis for the annual tax assessment, but you always have the option to change or supplement the information if it is not correct or complete. For securities not covered by the system, you must handle the reporting yourself.

The system can significantly ease the workload, especially if you have many transactions during the year or foreign custodian accounts. Because information is reported directly from banks and custodians, the risk of manual errors is minimized. You also get a comprehensive overview of your transactions, and if the information is complete, the system can automatically calculate and transfer gains or losses to your annual tax assessment. This saves you time and provides greater certainty that the tax calculation is correct.

The system does not cover all types of securities. Unlisted shares and bonds are not included, and if you have foreign custodian accounts, the Danish Tax Agency does not receive the information automatically. In these cases, you must report purchases and sales yourself with the necessary details to document acquisition costs and preserve the right to deduct losses. Even when information is reported automatically, errors or omissions can occur, so it is important that you verify the figures in your annual tax assessment.

The securities system registers corporate events such as stock splits, name changes, capital increases, and mergers. These events are included in the calculation of the average acquisition cost because they change the number of shares or their value. However, you should always verify that the system has handled the event correctly, as errors or omissions can occur. If you hold shares in foreign custodian accounts, it is your own responsibility to account for such changes in your calculations and reporting, as the system does not automatically have this information.