Banking Law and Mandate Agreements in Spain

1. Introduction

A mandate agreement (contrato de mandato) is an important concept in Spanish private law and has significant applications in banking. Under a mandate, one person—the mandante (principal)—entrusts another—the mandatario (agent)—with carrying out an act, service, transaction or management activity on the principal's behalf.

Article 1709 of the Spanish Civil Code provides the basic rule: under a mandate, one person undertakes to provide a service or perform something on the account or instructions of another. Spanish mandate law is principally contained in Articles 1709–1739 of the Civil Code.

In banking relationships, mandate principles can become relevant when a bank receives instructions to make payments, manage collections, operate accounts, execute transactions, administer assets or perform another financial operation for a customer.

Spanish banking contracts are often governed by specialised banking, payment-services and consumer rules as well. Therefore, mandate law does not replace banking regulation. Instead, Civil Code mandate principles frequently provide part of the private-law foundation for determining the bank's authority, duties and liability.

2. Legal Nature of the Mandate

The mandate creates an internal contractual relationship between the principal and the mandatary.

The essential elements normally include:

an instruction or entrusted activity;

acceptance by the mandatary;

performance for the account or benefit of the principal; and

an obligation to remain within the authority granted.

Article 1710 provides considerable flexibility. A mandate may be express or implied. An express mandate may be granted in a public document, private document or orally, while acceptance may also be express or inferred from the mandatary's conduct.

This flexibility is particularly significant in banking because authority can sometimes arise from the contractual relationship and the customer's conduct rather than from a separate document formally labelled "mandate."

However, proving the precise scope of an implied mandate can become difficult when a disputed banking transaction occurs.

3. Mandate and Representation Are Different

An important distinction in Spanish law is between mandato and representación.

A mandate creates the contractual obligation to perform an entrusted activity. Representation concerns the legal authority to act in another person's name toward third parties.

The Spanish Supreme Court has repeatedly recognised that the concepts are distinct.

In its Judgment 245/2026 of 17 February 2026, the Supreme Court again explained that mandate is a contractual relationship under which the mandatary acts for the principal, whereas voluntary representation originates from the granting of authority to represent another person. A mandate may exist with or without representation.

This distinction matters greatly in banking.

A customer might instruct a bank to carry out an operation for the customer's account. Separately, questions can arise concerning whether the bank or another person had authority to represent that customer legally in dealing with third parties.

4. General and Special Mandates

Article 1712 distinguishes between general and special mandates.

A general mandate covers the principal's affairs generally, while a special mandate concerns one or more specified transactions.

Article 1713 then imposes an important limitation: a mandate expressed in general terms ordinarily covers acts of administration. Express authority is required for certain acts of strict ownership or disposition, including transactions such as alienation and mortgages.

This rule has obvious banking significance.

Authority merely to administer someone's financial affairs should not automatically be interpreted as unlimited authority to dispose of valuable assets or undertake fundamentally different transactions.

5. Banking Accounts and Mandate Principles

The relationship between mandate law and bank accounts has been particularly important in Supreme Court jurisprudence.

Spanish case law has described the bank current-account relationship as an atypical contract to which rules governing civil mandate and commercial commission can be applied by analogy.

Consequently, when the bank executes instructions for its customer, questions may arise concerning:

whether an instruction actually existed;

who was authorised to issue it;

whether authority was express or implied;

whether the bank remained within the instruction;

whether the customer subsequently ratified the operation; and

whether the bank caused damage by incorrectly executing the mandate.

These questions determine whether the financial institution properly performed its contractual obligations.

6. Customer Instructions

The customer's instructions define the practical limits of many banking mandates.

Article 1714 establishes the fundamental principle that the mandatary cannot exceed the limits of the mandate. Article 1715 provides that the limits are not regarded as exceeded where the mandate is carried out in a manner more advantageous to the principal than specified.

For banks, this creates a straightforward principle:

A bank should execute the transaction that it has actually been authorised to execute, rather than substitute a materially different transaction on its own initiative.

For example, if a customer gives a bank a specific instruction concerning the application of funds, the legal issue may become whether that instruction was proved, whether the bank accepted it and whether the bank performed it correctly.

7. Implied Mandate

Banking disputes become more complicated when no written instruction exists.

Article 1710 permits implied mandates. But an implied mandate cannot simply be assumed whenever a transaction benefits the customer.

The surrounding conduct must demonstrate the existence of the necessary consent.

Long-standing banking practices between the parties can therefore become relevant evidence. Previous transactions, account statements, correspondence, objections or the absence of objections may all become relevant depending upon the circumstances.

The Supreme Court addressed precisely this problem in STS 67/2010.

The dispute concerned transactions from a bank account where written authorisation was not established. The courts considered the long history of transactions, receipt of account statements and lack of objection when deciding whether tacit consent existed.

8. Ratification

Ratification is another major principle.

A mandatary may sometimes carry out something beyond the authority originally granted. The principal can subsequently accept that transaction.

Ratification may be express or implied.

Spanish Supreme Court jurisprudence recognises that implied ratification can arise where the principal's conduct clearly demonstrates acceptance of the transaction or where the principal knowingly accepts its benefits.

This principle is important in banking because a customer who initially did not authorise a transaction might subsequently act in a way demonstrating acceptance.

Nevertheless, courts require sufficiently clear conduct. Mere ambiguity should not automatically be transformed into consent.

9. Duties of the Bank as Mandatary

Where mandate principles govern the relationship, several duties become important.

Compliance with Instructions

The bank should respect the customer's mandate and remain within the authority granted.

Appropriate Diligence

Banking institutions are professional operators. The contractual standard expected from them can therefore be demanding, particularly when handling customers' funds.

Accounting

Mandate law requires accountability concerning the activity performed on the principal's behalf.

In banking, account statements, transaction records and other documentation perform an important evidentiary function.

Return or Application of Funds

Money received for a specific purpose must normally be handled according to the contractual arrangement and applicable banking rules.

Liability

Failure to execute an accepted instruction properly can potentially create contractual liability if the necessary requirements—including breach, causation and legally recoverable loss—are established.

Important Spanish Case Law

1. Supreme Court Judgment 353/2008, 16 May 2008

This is particularly relevant to banking mandate law.

The proceedings concerned alleged failure to comply with instructions connected with payments relating to a mortgage loan. The dispute involved the contractual operation of a current account and whether instructions had actually been established.

The Supreme Court examined mandate principles in the banking context. The case demonstrates that liability cannot be imposed simply because the customer's desired financial result did not occur. The existence, scope and proof of the relevant instructions must first be established.

Legal importance: Banks can potentially be liable for failing to execute accepted instructions, but the customer must establish the relevant contractual and factual basis of the alleged mandate.

2. Supreme Court Judgment 67/2010, 11 February 2010

This case concerned disputed dispositions from bank accounts.

Although written authorisation for the relevant operations was not established, the circumstances included transactions extending over many years, delivery of account statements and the absence of objections.

The judgment discussed Articles 1710 and 1713 and the possibility of tacit consent. It also recognised the application by analogy of mandate and commercial-commission principles to the bank current-account relationship.

Legal importance: Authority in banking relationships is not invariably dependent upon a separate written mandate. Conduct may become relevant in establishing implied authority, although this is highly fact-specific.

3. Supreme Court Judgment 698/2003, 10 July 2003

This dispute concerned a bank and the management of instruments delivered for collection.

One party argued that the bank had accepted particular instructions concerning the destination of amounts collected. The Supreme Court concluded on the established facts that the bank had not consented to or accepted the alleged instructions concerning the use of those amounts.

Legal importance: Merely communicating a desired destination for money does not necessarily establish that the bank accepted a contractual mandate on those terms.

The existence of the mandate and its scope must be demonstrated.

4. Supreme Court Judgment 941/2005, 9 December 2005

This case involved a contractual relationship with a bank that was argued to contain elements of both the acquisition of a credit and a mandate relating to its recovery.

The proceedings illustrate that banking arrangements can possess a mixed contractual character rather than fitting perfectly into one traditional Civil Code category.

Legal importance: A court examines the substance of the banking arrangement rather than relying exclusively upon the label selected by the parties.

A banking contract may therefore contain mandate obligations alongside other contractual elements.

5. Supreme Court Judgment 1230/2007, 15 November 2007

This litigation involved BBV Privanza Banco and concerned a contract of mandate and a damages claim.

It illustrates the connection between mandate obligations and contractual liability.

Legal importance: If a professional financial institution undertakes an activity under a mandate and improperly performs the contractual obligation, the dispute can lead to a claim for damages, subject to proof of the applicable requirements.

6. Supreme Court Judgment 715/2010, 15 November 2010

The Supreme Court considered the determination of the object and scope of a mandate.

It explained that determining the object of the mandate is fundamentally a question of contractual interpretation. A conclusion reached by the lower court on contractual interpretation is not freely reopened on cassation merely because another interpretation might be possible; the demanding standards governing cassation review must be satisfied.

Legal importance: The exact wording and surrounding circumstances of the mandate are critical.

In banking litigation, parties should therefore distinguish carefully between:

what the customer wanted,
what the customer communicated, and
what the bank actually agreed to perform.

They are not necessarily identical.

7. Supreme Court Judgment 245/2026, 17 February 2026

A recent Supreme Court decision provides a particularly useful modern explanation of mandate and voluntary representation.

The Court distinguished the contractual mandate from the unilateral granting of representative authority and examined the consequences of termination, including the Civil Code rules dealing with death of the principal.

The judgment also reviewed substantial earlier Supreme Court jurisprudence concerning tacit mandates, ratification and the effects of transactions undertaken outside authority.

Legal importance: Mandate and power of representation must not be treated as automatically identical. This distinction can matter when determining whether someone was merely instructed to manage an affair or was also legally empowered to bind the principal toward third parties.

10. Exceeding the Mandate

Suppose a customer gives a bank authority to perform Transaction A but the bank performs Transaction B.

The first question is whether Transaction B falls within a reasonable interpretation of the original instruction.

If it does not, the bank may have exceeded its mandate.

The next questions include whether the customer subsequently ratified the transaction, whether the transaction created loss, whether another banking rule independently authorised the operation and whether the customer's own conduct contributed to the situation.

Therefore:

Exceeding authority does not automatically determine every question of liability, but it is usually the starting point of the analysis.

11. Revocation and Termination

Mandates are not necessarily permanent.

Civil Code Article 1732 identifies circumstances capable of terminating a mandate, while other provisions regulate revocation and its consequences.

Termination becomes particularly complicated where third parties are involved.

The Supreme Court's 2026 judgment reiterates the importance of Article 1738. In broad terms, transactions after termination may receive exceptional protection where both the mandatary is unaware of the terminating event and the third party acts in good faith. The Court emphasised that the statutory conditions must be satisfied together.

This can matter for banking powers of attorney.

Once a bank receives legally effective notice that authority has ended, subsequent transactions must be considered in light of that termination and the applicable account, representation and payment rules.

12. Mandate and Powers of Attorney in Banking

A mandate should also be distinguished from a power of attorney (poder).

Consider a customer who authorises another person to operate a bank account.

Several relationships may exist:

Customer–agent: the internal mandate determining what the agent is supposed to do.

Customer–bank: the banking contract determining how the account operates.

Agent–bank: the external exercise of representative authority.

An agent may therefore breach the internal mandate even where a transaction creates a different question regarding its external effectiveness toward the bank.

This separation between internal instructions and external authority is one of the most important concepts in Spanish mandate law.

13. Commercial Commission

Some banking activities may also resemble comisión mercantil, the commercial-law counterpart of mandate.

Consequently, Spanish banking jurisprudence sometimes refers to both Civil Code mandate rules and Commercial Code commission rules when characterising banks' obligations.

The correct classification depends upon the transaction.

A current account, securities transaction, collection arrangement and asset-management agreement should not automatically be treated as legally identical merely because each involves the bank following instructions.

14. Practical Banking Example

Assume a customer has €100,000 in an account and gives the bank written instructions:

Transfer €40,000 to Account X on 1 October.

The bank transfers €40,000 to Account Y instead.

The analysis would begin with the customer's instruction.

The instruction is specific. The bank's authority concerns a defined amount, recipient and transaction.

The principal legal questions would include whether the bank received and accepted the instruction, whether the deviation was authorised, whether the incorrect transfer can be reversed and whether the customer suffered recoverable damage.

Now consider a different situation.

For ten years, a customer permits a particular recurring account arrangement, receives statements showing the operations and repeatedly acts consistently with that arrangement.

If the customer later claims that no authority ever existed, the historical conduct may become relevant to whether tacit consent or ratification can be established. STS 67/2010 illustrates the importance of precisely this type of factual analysis.

15. Importance for Modern Banking

Mandate doctrine remains relevant even though banking has become increasingly digital.

Instructions that were historically delivered at a bank branch can now be issued through online banking, mobile applications and automated payment systems.

The technology changes, but many underlying legal questions remain familiar:

Who authorised the transaction?

What exactly was authorised?

Was authentication valid?

Did the bank execute the instruction correctly?

Did the transaction exceed the authority granted?

Was an unauthorised transaction subsequently ratified?

Was the mandate already revoked?

Modern payment-services legislation may provide specialised answers to some of these questions, particularly for payment authorisation and unauthorised transactions. Therefore, traditional mandate doctrine should always be considered together with the specialised banking regime applicable to the particular transaction.

16. Core Legal Principles from the Case Law

The Spanish jurisprudence supports several recurring principles.

First, mandate and representation are distinct concepts.

Second, the scope of the mandate is fundamental. A mandatary should not exceed the authority entrusted to it.

Third, mandates may be express or implied, but tacit authority must be established from sufficiently meaningful conduct.

Fourth, ratification can cure certain deficiencies in prior authority, including through unequivocal conduct in appropriate circumstances.

Fifth, banks may perform mandate-like obligations as professional financial intermediaries, particularly when executing customer instructions.

Sixth, the precise contractual classification depends upon the substance of the transaction. Banking arrangements can combine mandate with other contractual relationships.

Finally, special banking legislation prevails where it provides specific rules. Civil Code mandate doctrine consequently operates as part of a broader banking-law framework rather than as a complete regulatory system by itself.

Conclusion

Banking law and mandate agreements in Spain are closely connected because banks routinely perform transactions on customers' instructions.

The fundamental legal framework comes from Articles 1709–1739 of the Spanish Civil Code, particularly the rules concerning creation of mandates, express and implied authority, general and special mandates, limits of authority, performance, ratification and termination.

Spanish Supreme Court jurisprudence—including STS 698/2003, STS 941/2005, STS 1230/2007, STS 353/2008, STS 67/2010, STS 715/2010 and STS 245/2026—shows how these principles operate in practice, including in disputes involving banks and financial transactions.

The central principle is straightforward: a bank or other mandatary must identify the authority it has received, remain within that authority and properly perform the entrusted transaction. Where authority is disputed, Spanish courts examine the contractual terms, instructions, conduct of the parties, possible tacit consent or ratification and the specialised banking rules applicable to the transaction.

This makes mandate law an enduring part of Spanish banking law, despite the transition from traditional branch banking to electronic and automated financial services.