Using a self-built Excel solution to manage and report leasing agreements in accordance with IFRS 16 can pose certain difficulties. Here are some of the potential issues:

1. Incorrect formulas and calculations: A common issue with self-built Excel solutions is incorrect formulas and calculations, which can result in erroneous reporting and accounting of lease agreements.

2. Risk of manual errors: As a self-built Excel solution requires manual handling of data, there is a risk of manual errors, especially when dealing with large amounts of data.

3. Lack of data protection: Excel documents can be sensitive and contain confidential information, but they do not always provide sufficient protection for corporate data. If a self-built Excel solution is used to manage lease agreements, this can pose a security risk.

4. Difficult to create reports: Creating reports and compilations of data from a self-built Excel solution can be time-consuming and difficult, especially if the data is in multiple sheets or workbooks.

5. Limited opportunities to automate the process: A large number of lease agreements and complex calculations can make manual work inefficient or insufficiently precise. With a self-built Excel solution, it can be difficult to automate the process, which can lead to increased risk of incorrect reporting.