Can the owner raise the rent without warning?
During the term of the lease, the lessor may only raise the rent on the date on which each year of the contract is fulfilled. In addition, you can only increase the rent if your update was expressly agreed and the terms for it were set. If, on the contrary, there is no update clause in the contract, the landlord may not demand any rent increase from its tenant.
Suppose, for example, that a lease is signed on January 1, 2020 and that it was agreed that the rent could be updated according to the annual variation of the Consumer Price Index (CPI). In this case, on January 1, 2020, the lessor can update the rent by applying the CPI variation rate published by the National Statistics Institute.
In addition, to raise the rent to the tenant, the landlord will have to notify the tenant in writing of the amount of the updated rent, identifying the percentage of alteration applied and accompanying it, if the tenant asks for it, with the certification of the National Statistics Institute that reflect the corresponding percentage variation.
The landlord can make this notification by email, provided that an electronic address has been indicated for this purpose in the lease, by burofax, certified mail with acknowledgment of receipt and it is even admitted that it be made by note on the receipt of monthly payment of rent.
Once the tenant receives in writing the amount of the updated rent will be obliged to pay the same from the month following the receipt of the notification. For example, if the landlord notifies his tenant on November 2 of the amount of the updated rent, the tenant will have to pay that new amount from the following month, in this case, December.
Finally, we warn that, after the last modification of the Urban Leasing Law, since March 6, 2019, it is not allowed to include in the housing lease agreements an agreement on rent update that sets a percentage of variation above from the one I experienced from the CPI. If this index increases by 0.1% annually, this will be the maximum percentage that the landlord can apply to update the rent.