What is an extension?

Extending a short-term lease means prolonging the contract beyond its original end date while keeping the legal framework of a short-term lease. It differs from renewal (a new lease) and tacit continuation (continuing without any formality).

Under Belgian law, the extension is the only mechanism that allows a short-term lease to be prolonged without converting it into a 9-year lease. It requires an explicit, written agreement between landlord and tenant, formalised as an addendum to the contract.

The fundamental condition: the total duration of the lease (initial term plus extensions) must never exceed 3 years. Beyond that, the lease is automatically reclassified as a 9-year primary residence lease.

Conditions and formalities

For an extension to be valid and avoid reclassification, several conditions must be met:

Maximum total duration of 3 years: initial lease plus all cumulative extensions. A one-year lease extended twice for one year each reaches the ceiling.

Mandatory written addendum: the extension must be formalised in a written document signed by the landlord and tenant. The addendum must state:

  • The reference to the original lease (date, registration number).
  • The new end date.
  • Any changes (rent, charges).
  • A statement that all other clauses remain unchanged.

Signature before expiry: the addendum must be concluded before the current lease ends. After expiry, the tenant is in a situation of remaining in the premises.

Registration: the addendum must be registered with the FPS Finance within 2 months of signing, via MyRent (free). Registration is mandatory, just as for the main lease.

Number of extensions: the law does not set a limit. You may extend 2 times, 3 times, or more, as long as the total duration stays within 3 years.

Consequences if the extension is not formalised

Failure to formalise is the most common pitfall. If the tenant remains in the property after expiry without a signed addendum:

Tacit continuation as a 9-year lease: the lease is automatically deemed to be a 9-year primary residence lease, considered to have started on the date of the original lease.

Practical consequences:

  • The tenant benefits from all protections of a 9-year lease.
  • The landlord can no longer freely terminate at the end of the term.
  • Termination conditions change dramatically (6-month notice for personal occupation, compensation requirements).
  • The remaining duration is calculated from the original start date.

A simple text message or email is not enough. Case law requires a formal document signed by both parties. An informal exchange does not constitute a valid extension.

To secure your extensions, our online lease creator generates compliant addenda in minutes.

In practice: managing the extension properly

To avoid any risk of reclassification, follow these steps:

  1. Plan ahead: contact the tenant at least 3 months before expiry to discuss the renewal.
  2. Check the calendar: calculate the total duration (initial lease plus planned extension). If it exceeds 3 years, a new 9-year lease will be necessary.
  3. Draft the addendum: mention the references of the original lease, the new end date, and any changes.
  4. Sign together: the addendum must bear the signature of both parties.
  5. Register: submit the addendum on MyRent within 2 months.

Can the rent be changed? Yes, during the extension, the parties may agree on a new rent. This change must be stated in the addendum.

For the rules on terminating a short-term lease or the maximum duration, see our dedicated guides.