A lease amendment (aditamento) is a written agreement that changes one or more clauses of a lease that has already been signed, leaving in force everything that is not expressly modified. It can be used, for example, to change the rent by agreement, extend the term, add a guarantor or correct details. It should identify the original lease, state exactly what changes, set the date it takes effect and be signed by the parties affected.
- In practice, aditamento and adenda are both used for a document that supplements or changes the lease.
- A material change should not live only in an exchange of messages: put it in writing, date it and collect the necessary signatures.
- If you are changing the parties or the very subject of the lease, it may be safer to sign a new lease.
- If the change affects details declared to the Tax Authority (AT), confirm the applicable procedure on the Portal das Finanças.
What does “aditamento” mean in a lease?
An aditamento works as an extra layer on top of the lease. Instead of copying every clause into a new document, the parties state which points they replace, add or remove. The original lease continues to be read together with the amendment.
The name of the document matters less than its content. You can call it an “Aditamento”, an “Adenda” or an “Amendment agreement”, as long as it is unambiguous: who agreed, which lease it refers to, what changes and from when.
When should you make a lease amendment?
| Change wanted | Amendment? | Watch out |
|---|---|---|
| Extend the term by agreement | Usually, yes | State the new end date and the renewal rules (see the notice periods for opposing renewal). |
| Change the rent by agreement | Yes | Don’t confuse this with the annual rent update provided for by law or the lease: to work out the figure, use the rent update calculator. |
| Add or release a guarantor | Yes | The guarantor and the other parties must expressly accept the new wording. |
| Allow pets, works or a specific use | Yes | Set limits, responsibilities, reinstatement and any annexes. |
| Correct a slip in the address, property register article or identification | Yes | Check whether the correction also has to be reflected with the AT. |
| Fully replace the landlord or the tenant | Depends | A change of party may follow from the law or require a new lease; get legal validation for your specific case. |
| Change the rented property | As a rule, a new lease | The essential subject of the agreement is no longer the same. |
If you are still preparing the initial document, use the lease agreement generator. If you need to check the full structure, see the annotated lease template.
What should the amendment include?
- Title and number of the amendment. Example: “First amendment to the residential lease”.
- Identification of the parties. Name, NIF (tax number), identification document and the capacity in which they act.
- Reference to the original lease. Date, address of the property and, where one exists, the registration number or any details that remove all doubt.
- Amended clauses. Write out the new wording in full. Avoid vague phrases such as “the term changes as agreed”.
- Effective date. Say from which day the new wording applies.
- Continuity clause. Confirm that everything that has not been changed remains in force.
- Date and signatures. Give each party a copy and keep one with the original lease.
Lease amendment template
The template below is a starting point. Remove the options that do not apply and ask for professional review when the change involves assignment, transfer, guarantees, breach or a dispute. It is given in English for convenience: if your lease is in Portuguese, have the amendment drafted in the same language.
Between:
1. [LANDLORD’S NAME], NIF [NIF], residing at [ADDRESS], hereinafter the “Landlord”;
and
2. [TENANT’S NAME], NIF [NIF], residing at [ADDRESS], hereinafter the “Tenant”;
this amendment to the lease agreement signed on [DATE], concerning the property located at [FULL ADDRESS], is entered into under the following clauses:
Clause 1 — Amendment
Clause [NUMBER] of the lease shall read as follows:
“[QUOTE THE NEW WORDING IN FULL]”.
Clause 2 — Effective date
The amendment takes effect on [DATE].
Clause 3 — Lease otherwise unchanged
All clauses of the original lease that are not expressly amended by this amendment remain fully in force.
Made in [NUMBER] copies, one for each party.
[PLACE], [DATE]
The Landlord: ____________________
The Tenant: ____________________
[The Guarantor, if applicable: ____________________]
Do you need to notify the Finanças of the amendment?
It depends on what was changed. The AT keeps information on the urban lease and offers its own operations on the Portal das Finanças. When the amendment changes details that appear in the lease as reported — for example the rent, the duration or the identification of the parties — confirm the correct operation before treating the process as complete. A merely private change does not automatically correct the tax record.
Mistakes that make a change hard to prove
- not identifying the original lease or the property;
- saying only “the clause changes”, without quoting the new wording;
- not obtaining the signature of a person directly affected;
- not setting the date the change takes effect;
- changing a guarantee without the guarantor’s involvement;
- keeping the amendment separate from the lease and its annexes;
- ignoring the update that is needed on the Portal das Finanças.
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Frequently asked questions
What is the difference between an aditamento and an adenda?
In contract practice the two terms are often used as equivalents. What matters is that the document identifies the original lease and says, unambiguously, what is added or changed.
Does an amendment have to be signed by both landlord and tenant?
An agreed change should be signed by the parties whose rights or obligations change. If it affects a guarantee, the guarantor should also take part. A unilateral change is only possible where the law or the lease itself allows it and the applicable procedure is followed.
Can I change the rent through an amendment?
Yes, when the parties have validly agreed. This is different from the annual rent update: that update follows its own rules on calculation and notification.
Is it possible to change the tenant’s name with the Finanças?
Don’t treat replacing a tenant as a simple administrative correction. First work out whether there is a legal transfer, an accepted assignment or a need for a new lease; then reflect the correct solution on the Portal das Finanças.
Does the amendment replace the original lease?
No, unless the document expressly says otherwise. Normally the original lease stays in force, read together with the changes in the amendment.
Official sources consulted: Portal das Finanças — urban lease agreement; Law no. 6/2006 (NRAU, the New Urban Lease Regime); Decree-Law no. 160/2006. Updated on 12 September 2026.
