Co-owner refuses to sell in Spain: who must get the MASC request?

If a co-owner refuses to sell property in Spain, whether it is a sibling who inherited with you or an ex-partner, the usual way out is a court claim to force the division or sale: the acción de división de la cosa común (a partition action). Since 2025, under Organic Law 1/2025, the court will not admit that claim unless you first tried an out-of-court step called a MASC (medio adecuado de solución de controversias, an appropriate means of out-of-court dispute resolution). A 2026 ruling of the Provincial Court of Bizkaia answers a very practical question about that step: who exactly has to receive your request? The case involved a block of flats rather than siblings, but the reasoning is the part that matters. For the wider picture, see my guide to the court route when inherited property is shared between siblings and my page on dissolving co-ownership in Spain.

An order (Auto) of the Provincial Court of Bizkaia, section 3, of 18 March 2026, settles a very practical point in a partition action: is it enough to send the MASC to the co-owner who really opposes the division, or must it go to all the co-owners?

This case was a little unusual. It concerned a community of owners in a block of flats (think of a Spanish sitcom about a building full of neighbours), not the typical flat held in undivided shares (proindiviso) between several siblings. But it is just as useful, because the action to untangle the problem is the same: the action to divide the jointly owned property.

The case: a claim to divide a jointly owned property was not admitted

The proceedings began with a claim filed by several co-owners.

Mr Alejo and five other co-owners filed an ordinary claim bringing a partition action against the other co-owners of a building in Bilbao, asking for the division of an upper-floor flat.

“D. Alejo y otros cinco copropietarios, presentaron una demanda de juicio ordinario ejercitando acción de división de cosa común frente a los demás copropietarios del edificio sito en Bilbao, […], solicitando la división de planta alta […], vivienda […].”

The court did not admit the claim at first.

The court, by order of 15 January 2025, refused to admit the claim because it considered that compliance with the procedural requirement set out in article 5 of Organic Law 1/2025 had not been shown.

“El juzgado, por auto de fecha 15 de enero de 2025, no admitió a trámite la demanda por considerar que no constaba acreditado el cumplimiento del requisito de procedibilidad establecido en el artículo 5 de la Ley Orgánica 1/2025.”

What does the MASC rule say before you sue a co-owner?

The Provincial Court recalls the rule introduced by Organic Law 1/2025 (“LO 1/2025”):

Article 5 of LO 1/2025 provides that, in the civil courts, as a general rule, for a claim to be admissible it is a procedural requirement to have first resorted to one of the appropriate means of dispute resolution (MASC) set out in article 2.

“el art. 5 de la LO 1/2025 establece que, en el orden jurisdiccional civil, con carácter general, para que sea admisible la demanda se considerará requisito de procedibilidad acudir previamente a algún medio adecuado de solución de controversias (MASC) de los previstos en el artículo 2.”

It also gives the legal definition of a MASC:

That provision defines the MASC as “any type of negotiating activity, recognised in this or other laws, whether national or regional, to which the parties to a conflict resort in good faith in order to find an out-of-court solution to it, either by themselves or with the intervention of a neutral third person”.

“Dicha norma define el MASC como «cualquier tipo de actividad negociadora, reconocida en esta u otras leyes, estatales o autonómicas, a la que las partes de un conflicto acuden de buena fe con el objeto de encontrar una solución extrajudicial al mismo, ya sea por sí mismas o con la intervención de una tercera persona neutral».”

How do you prove you tried to negotiate?

The order also reminds us that the attempt to negotiate has to be provable.

Article 10 of LO 1/2025 provides, as far as relevant to resolving the appeal, that in order to show that a prior negotiation has been attempted and to meet the procedural requirement, that negotiation, or the attempt at it, must be recorded in a document.

“el art. 10 LO 1/2025 establece, en lo que interesa para la resolución del recurso, que, a los efectos de acreditar que se ha intentado una actividad negociadora previa y cumplir el requisito de procedibilidad, dicha actividad negociadora o el intento de la misma deberá ser recogida documentalmente.”

Where no neutral third person is involved, the ruling explains how the attempt can be shown:

The attempt to negotiate may be shown by any document proving that the other party received the request or invitation to negotiate or, where applicable, the proposal, on what date, and that they were able to access its full content.

“podrá acreditarse el intento de negociación mediante cualquier documento que pruebe que la otra parte ha recibido la solicitud o invitación para negociar o, en su caso, la propuesta, en qué fecha, y que ha podido acceder a su contenido íntegro.”

It also recalls when the process can be treated as ended without agreement:

The process will be understood to have ended without agreement, among other alternatives, if thirty calendar days pass from the date the other party received the initial request to negotiate and the first meeting or contact aimed at reaching an agreement has not taken place, or no written reply is obtained.

“se entenderá que se ha producido la terminación del proceso sin acuerdo, entre otras alternativas, si transcurrieran treinta días naturales a contar desde la fecha de recepción de la solicitud inicial de negociación por la otra parte y no se mantuviera la primera reunión o contacto dirigido a alcanzar un acuerdo o no se obtenga respuesta por escrito.”

Must the negotiation cover the same issue as the lawsuit?

Another relevant point is that the prior negotiation has to be connected with what you later ask for in the claim.

Another of the demands of the procedural requirement, found in article 5 of LO 1/2025, is the identity that must exist between the subject of the negotiation and the subject of the lawsuit, even though the claims that might be brought in court on that subject may vary.

“Otra de las exigencias del requisito de procedibilidad, que se localiza en el art. 5 de la LO 1/2025, es la identidad que habrá de existir entre el objeto de la negociación y el objeto del litigio, aun cuando las pretensiones que pudieran ejercitarse, en su caso, en vía judicial sobre dicho objeto pudieran variar.”

The court also recalls that the negotiation can be carried out directly or through a lawyer:

In particular, the requirement will be considered met when the negotiating activity is carried out directly by the parties, or between their lawyers acting under their instructions and with their consent, as well as in cases where the parties have used a collaborative law process.

“Singularmente, se considerará cumplido el requisito cuando la actividad negociadora se desarrolle directamente por las partes, o entre sus abogados o abogadas bajo sus directrices y con su conformidad, así como en los supuestos en que las partes hayan recurrido a un proceso de Derecho colaborativo.”

Do you have to attach proof of the MASC to the claim?

The order links this requirement to the Civil Procedure Act (Ley de Enjuiciamiento Civil, “LEC”).

Article 264 LEC has been amended, and it now provides that the claim must be accompanied by the document showing that the negotiation prior to going to court was attempted, when the law requires that attempt as a procedural requirement.

“se ha modificado el artículo 264 LEC, en el que ahora se establece que habrá de acompañarse a la demanda el documento que acredite haberse intentado la actividad negociadora previa a la vía judicial cuando la ley exija dicho intento como requisito de procedibilidad.”

And it adds:

Similarly, the new article 399.3 LEC requires the claim to state a description of the prior negotiation carried out, or the impossibility of it, and to list, where applicable, the documents showing that an appropriate means of dispute resolution was used, except in the cases the law exempts from this procedural requirement.

“En similar sentido, el nuevo art. 399.3 LEC exige que se haga constar en la demanda la descripción del proceso de negociación previo llevado a cabo o la imposibilidad del mismo, y se manifestarán, en su caso, los documentos que justifiquen que se ha acudido a un medio adecuado de solución de controversias, salvo en los supuestos exceptuados en la Ley de este requisito de procedibilidad.”

Do you have to send the MASC request to every co-owner?

In this specific case, the claimants did not send the MASC to all the co-owners.

The claimant argues that it sent the MASC only to this co-owner, because it understands he is the only one of them who has been opposing the division of the property that is sought.

“La parte actora aduce que únicamente remitió el MASC a este comunero, por entender que es el único de todos ellos que viene oponiéndose a la división del inmueble pretendida.”

The Provincial Court looks at the context:

Having reviewed the minutes of the owners’ meeting of 9 March 2017, it can be seen that all the owners of the community voted in favour of selling the so-called “porter’s flat”, of which they are all owners, except the co-owner mentioned, who voted against, and the owner of a flat on another staircase.

“revisada el acta de la Junta de Propietarios de fecha 9 de marzo de 2017, se observa que todos los propietarios de la Comunidad votaron a favor de la venta del llamado «piso del portero» del que todos son titulares, salvo el citado comunero que votó en contra, además del propietario del piso de la escalera […].”

Later, the claimant sent a confidential binding offer:

On 22 May 2025, with the aim of meeting the procedural requirement under analysis, it sent a confidential binding offer in order to reach an out-of-court agreement.

“con fecha 22 de mayo 2025, con el objetivo de cumplir con el requisito de procedibilidad analizado, remitió oferta vinculante confidencial a fin de alcanzar un acuerdo extrajudicial.”

And the court considers that it was received:

It seems clear, therefore, that the message containing the offer was properly received by the defendant, in the form required by article 5 LO 1/2025.

“Parece claro, por tanto, que el mensaje con la oferta fue correctamente recibido por el demandado, en la forma requerida por el artículo 5 LO 1/2025.”

Is it enough to write to the co-owner who objects?

The Provincial Court’s conclusion is especially useful for partition proceedings with several co-owners.

The Chamber considers that this out-of-court demand, sent to the only co-owner who opposes the partition action brought, when all the others have voted in favour at the corresponding owners’ meeting, is sufficient for the purposes of article 10 LO 1/2025, since he is the only one to whom the offer of a negotiation must be sent.

“la Sala estima que esta reclamación extrajudicial, remitida al único comunero que formula oposición a la acción de división ejercitada, cuando todos los demás han votado a favor en la Junta de Propietarios correspondiente, es suficiente a los efectos prevenidos en el art. 10 LO 1/2025, por cuanto es el único al que se debe enviar la oferta de una negociación.”

The court adds a practical reason:

To understand it otherwise would mean having to send the negotiation offer even to those who are claimants in these proceedings.

“Entender lo contrario supondría la necesidad de enviar la oferta de negociación incluso a quienes son demandantes en el presente procedimiento.”

And it concludes that the earlier communication did its job:

That communication performs the functions of a true offer to resolve the conflict by the least burdensome route possible, which is what the MASC regulated in articles 3 and 5 LO 1/2025 and 264.4 and 399 LEC is.

“la citada comunicación cumple las funciones de una verdadera oferta de resolver el conflicto por la vía menos gravosa posible en lo que es el MASC regulado en los artículos 3 y 5 LO 1/2025 y 264.4 y 399 LEC.”

What this means when a co-owner refuses to sell

In this ruling, the Provincial Court of Bizkaia held that the out-of-court demand sent to the co-owner who opposed the partition action was enough for the procedural requirement of LO 1/2025. What was decisive was that all the other co-owners had voted in favour of the sale, and that the offer went to the person who really kept the dispute alive.

So before you file a partition claim to leave the proindiviso, the MASC stage has to be done with particular care. It is not only a matter of trying to negotiate, but of being able to show in documents what was proposed, to whom it was sent and why that person was the one blocking the solution.

I have studied thousands of co-ownership dissolutions in Spain, and I work with clients in English. If you are heading towards a forced sale, my guide to inherited property shared with siblings shows where this step fits in the whole court route.