There are no specific rules regarding the retention of your employment contracts. However, as is the case for many administrative documents, it is advisable to keep them for, at least, the term of your employment related to the contract and a number of years afterwards. It is, indeed, always useful to be able to compare your income and fringe benefits between one employer and another. In case of dispute with your employer, you can always refer to the content of your contract to justify and document events or matters concerning your employment.
See also https://www.izimi.be/faq/faut-t-il-garder-ses-contrats-de-travail [how long do you have to keep your employment contracts]
Retention period for employment contracts
The management and retention of your employment contracts is not regulated by law. It requires, above all, common sense and prudence. We would suggest keeping your employment contracts for your entire professional life.