Conflicts of interest: how to check before you take a matter

In most small firms, the conflict check is someone asking down the corridor: “does anyone know this company?”. It works while the firm has three lawyers with good memories and ten years of history. It stops working the day a fourth lawyer joins, or the day the name that matters is not the company’s but its director’s.

The rules leave little room. Article 51 of the Estatuto General de la Abogacía Española (the General Statute of the Spanish Legal Profession, approved by Real Decreto 135/2021) requires lawyers not to defend interests in conflict with their client’s “or with their own”. Article 12 of the 2019 Código Deontológico (Code of Conduct) says the same in more detail. And since Ley Orgánica 5/2024 on the Right of Defence, article 19.2 puts it in an organic law: lawyers shall not take on a defence or advise in matters where there is a conflict of interest, in accordance with the statutory rules.

None of these texts tells you how to check. That part is the firm’s job.

What the rule actually prohibits

The five paragraphs of article 51 are worth keeping to hand, because each maps to a different question at intake:

1. General rule. Do not defend interests in conflict with the client’s or with your own.
2. Several clients in one matter. You may not act for two or more clients in the same matter where there is a conflict or a “significant risk” of conflict between them, unless all of them authorise it expressly and in writing after being properly informed, and only in non-contentious matters. Acting for all parties as a mediator or in drafting contractual documents is allowed, with strict neutrality.
3. Conflicts that arise later. If a conflict arises between two clients, you must stop acting for both, unless both authorise you in writing to continue for one of them.
4. Former clients. You must decline a new client where there is a risk of breaching confidentiality over what a former client told you, or where what you know from that former client’s other matters could unduly favour the new one.
5. Collective practice. Where several lawyers practise collectively or belong to or work with the same firm, whatever its legal form, the rules apply to the group as a whole and to each of its members.

Article 12 of the Code of Conduct, in section C, adds points that weigh heavily in practice. For former clients it asks you to consider the nature of the matters and the time elapsed, and it forbids, in every case, acting against a former client in the same proceedings in which you defended them, including ancillary steps, appeals and enforcement. It also forbids taking a matter when the opposing party has already consulted you on it and you obtained information that compromises your independence, confidentiality or loyalty.

That last point is the one most often forgotten, and it is where this article’s view comes from.

The check comes before the first meeting, not after

If the firm listens first and checks afterwards, it has already received confidential information from someone who may not be able to become a client. And that information contaminates: if the other side calls the following week, the firm cannot act for them either. It has lost both matters purely through the order in which it did things.

So the conflict check is not a step in the engagement letter; it belongs to the first contact. When the appointment is requested, collect names only: who is consulting, against or with whom, and what kind of matter. No detail on the merits. Search on that, and only then listen.

Who to search for

The classic mistake is to search only the client’s name. A useful search covers, at minimum:

• The client, in every variant: full name, tax ID, previous company name, trading name.
• The opposing party, which is the search that actually catches conflicts.
• Related parties on each side: a spouse in a family matter, guarantors, co-defendants, insurers.
• The corporate group: parent, subsidiaries and sister companies. A firm that regularly advises a subsidiary will struggle to sue the parent without damaging the trust paragraph 1 requires.
• Directors and significant shareholders of the companies involved. People move between companies; conflicts follow them.
• The firm’s own interests: a partner with a stake in the opposing company, a relative on its board, a lawyer who previously worked for the other side.

For this to be possible, the firm needs a single client and contact database that includes closed matters. If old clients live in a retired partner’s spreadsheet and contacts in each lawyer’s inbox, the search finds nothing. The piece on legal CRM covers how to structure it.

There is a useful overlap with due diligence under Ley 10/2010, Spain’s anti-money-laundering law. Where a matter falls within its scope, identifying the client and its beneficial owner already requires collecting exactly the names the conflict search needs. Doing both on the same intake form saves work and stops one being done without the other. See the article on KYC for lawyers.

A case: the seller was a former client

A four-lawyer firm in Málaga receives an appointment request on Monday 6 July 2026. A Norwegian buyer wants to purchase a house for €640,000. The seller is a small local development company, a sociedad limitada.

The request form captures three names: the buyer, the selling company and its sole director, taken from the Companies Register. The search on the company returns nothing. The search on the director does: in 2023 one of the firm’s partners advised him on refinancing that same company’s debt. The file is closed.

It is not the same matter, so the absolute bar in article 12.C of the Code of Conduct (never act against a former client in the same proceedings) does not apply. Paragraph 4 of article 51 does: the firm knows the seller’s financial position, its maturities and how much room it has to negotiate. That knowledge would unduly favour the buyer when negotiating price or guarantees. And three years have passed, not fifteen.

It does not matter that the partner who handled the refinancing would not touch the purchase. Paragraph 5 extends the conflict to the whole firm, and in a four-person practice sharing a server and a coffee machine, no internal barrier will convince anyone.

Decision: the matter is declined, the buyer is told without any explanation that would reveal anything about the former client, and is given the names of other firms. Total time: twenty minutes, before the buyer said anything about her financing or the maximum price she would pay. Had the search been run after the meeting, the firm would have been contaminated on both sides. The article on property purchases explains why the buyer’s lawyer sees so much of the other side in a deal like this.

When the conflict appears mid-matter

Sometimes the initial check was done properly and the conflict appears later: a new co-defendant joins, the opposing party merges with a regular client, two shareholders the firm advised jointly fall out.

Paragraph 3 of article 51 is clear: if the conflict is between two clients, you stop acting for both, unless both authorise in writing that the firm continues for one. In practice that means three steps:

1. Stop work on anything that is not urgent, and record the date the conflict was identified.
2. Inform both clients in writing, without revealing either one’s information to the other, and propose the paragraph 3 authorisation where it makes sense.
3. Protect running deadlines while the client finds another lawyer. Withdrawing does not license you to let a deadline lapse, and one that expires mid-handover is the most predictable complaint of all.

The criminal boundary

Article 467.1 of the Spanish Criminal Code punishes with a fine of six to twelve months’ day-units and a two-to-four-year professional disqualification any lawyer or procurador who, having advised or defended someone, defends or represents in the same matter a party with opposing interests without the first client’s consent. The criminal perimeter is narrow: same matter, opposing interests, no consent. The ethical one is much wider. A case falling short of article 467 is not thereby permitted under article 51.

How this fits in Mandato

In Mandato, clients, contacts and the parties to each matter sit in a single client database, closed matters included. The search that took twenty minutes in the example runs against that same database, history included, before the matter is opened. The tool finds matches; whether there is a conflict remains the lawyer’s decision, and it is worth recording on the matter with its date.

The full text of the General Statute is on the BOE.