No need for bills.

Not so sure...

If you are sued by the evicted tenant, how do you will prove the total amount of money you have spent for those renovation works?

In this case, 3 years of rent = 3 * 799,91 * 12 = 28.796,76 €

- if you perform renovation works (the official bills of those renovation works must be higher than 2 years of rent)

Wrong. No need for bills. On peut faire soi-même une estimation des coûts. Par ailleurs, si je ne me trompe pas et si c'est des travaux dans un seul appartement, c'est trois années de loyer et fin du bail à une échéance triennale.

Yes, it is still the same tenant/same apartment. Since first contract was signed for one year for trial, I assumed we need to make a new contract as the first one expired.

You are fully wrong!

In order to protect the Tenant's rights, if you don't break the contract 3 months (at least) before the end of the given trial period (1 year), the contract is automatically transformed into the standard Belgian main residence contract (9 years). 

So now you are legally obliged to keep your tenant until 2021.

You can only evict her
- by paying to her 18 months of rent
- if you need the apartment for a member (first degree) of your family. Your tenant can sue you, if the member of your family doesn't have his/her main residence there for 2 years at least
- if you perform renovation works (the official bills of those renovation works must be higher than 2 years of rent)

How does one renew a rental contract?  Just change/extend the date on original contract?

...

My options now are, if I want the tenant to leave:
A) send a registered termination note with 3 months notice before expiry of nine year lease
B) send a registered termination note with 6 months notice if we need the apartment for our family or for repairs, right?

In  the same way, can she walk out without giving any notice ?

Just register the first contract.

A is right
B is right but there are conditions

Once the contract is registered, she must send a registered termination note with 3 months notice

I did not realize the contracts you mentionned where all for the same tennant and same appartment...

In this case, you are of course outlaw...

You can renew a short term contract of résidence principale only ONCE! And contract condition can not be changed...

Yes, it is still the same tenant/same apartment. Since first contract was signed for one year for trial, I assumed we need to make a new contract as the first one expired.

For renewal,  no contract conditions were changed. we simply printed a new template, revised the date, added any indexed rent for that year :
Didn't   putting the revised indexed rent is a change of condition.
WE always kept the index reference to the first contract.

How does one renew a rental contract?  Just change/extend the date on original contract?
Myself and my tenant, we both assume we have a nine year contract now,  started in 2012 and finishing in 2021?

Our first contract signed in 2012, although was limited to one year, is still valid and right?
My options now are, if I want the tenant to leave:
A) send a registered termination note with 3 months notice before expiry of nine year lease
B) send a registered termination note with 6 months notice if we need the apartment for our family or for repairs, right?

In  the same way, can she walk out without giving any notice ?

In this case, you are of course outlaw...

You can renew a short term contract of résidence principale only ONCE! And contract condition can not be changed...

Formule légale utilisée
Nouveau loyer (octobre 2017) = Loyer de base (septembre 2012) * IS [2004] septembre 2017 / IS [2004] août 2012
Ce qui donne en chiffres:
799,91EUR = 750,00 EUR * 127,42/ 119,47     ce nouveau loyer est valable à partir de octobre 2017

Si je ne me trompe pas, l'indice de départ est celui du mois qui précède celui durant lequel le bail a été conclu et donc dans le cas présent août 2012.

IF it is a main residence contract!

So in your case, only the first contract is legally valid and shall be indexed.

You need to know:
1/ When the contract has been signed: 8th of September 2012
2/ When the contract has started: 1st of October 2012

Then 799,91EUR  is the new legal rent as of October 2017

I always put a print out of the official rent calculator published by the Belgian authorities

The confusion here is, I am still calculating indexation,  based on base rent and index from very first contract sign date whereas, looks like she took the 4th final renewed contract to "service des locataires de Bruxelles" and claims she will only pay indexation from May 2018 :-/

I will push her that she needs to pay from October 2017. Thanks for your help  Grmf!

So, the data for the first contract are as follow:

2) When can I ask for it ?
Any time. But when you ask for it, the request is valid only 3 months backward. The normal time is on anniversary.

3) What indexed rent should I ask for?
I don't get your question. You put the valid numbers and dates in the calculator, ask join the result to the letter you send to your tennent.

I am a landlord; I have renewed  rental contract 4 times, with my tenant X, in Brussels capital region,  as follows:
This has become a  9 year contract  VALID UNTIL 2021, and we have been using PIMS contract templates in all these four renewals.

I use http://statbel.fgov.be/en/statistics/fi … alculator/ to calculate current index but I am lost now  on what should be my base rent and what is the indexation value, should it based on the very first contract on 2012 or the last contract signed in 2015.

1) How to calculate indexation?
2) When can I ask for it ?
3) What indexed rent should I ask for?