The 2026 Annual Tax and Customs Control Plan is expected to be released in late February or mid-March. As usual, it will outline the Spanish Tax Agency’s enforcement priorities for the year, with a strong focus on ensuring tax compliance. As in previous years, the Plan is likely to include a specific section on related-party transactions, together with increased scrutiny of transfer pricing arrangements.

Against this backdrop, it is worth highlighting the types of transactions that most frequently give rise to disputes in practice, particularly among small and medium-sized enterprises.

1. Intragroup sales of goods

When reviewing intragroup sales, the Tax Agency typically focuses on three key areas.

a) Functional analysis and risk profile

A clear and well-documented functional analysis is essential. This means identifying, for each party involved, the functions performed, the assets used, the risks assumed, and the actual value contributed. One of the main points of review is whether the profitability earned is consistent with the entity’s functional profile.

b) Segmentation of results

Even if an entity’s overall profitability falls within market ranges, the Tax Agency may still challenge specific margins if, once results are broken down by business line or type of transaction, material deviations emerge. A robust, well-segmented accounting analysis—separating related-party transactions from third-party dealings and clearly distinguishing different business activities—is therefore critical. Poor segmentation is a common trigger for audit disputes.

c) Selection of comparables

Benchmarking remains one of the most contentious areas. Disagreements often arise around how comparables are selected or rejected. A consistent methodology, a traceable search process, and solid supporting documentation are key to defending the taxpayer’s position.

2. Intragroup services

Intragroup services continue to be an area with a high adjustment risk.

a) Benefit test

The Tax Agency may question whether services provided by a parent company genuinely benefit its subsidiaries or whether they should be treated as shareholder services. Taxpayers must be able to evidence that the services were actually provided, that the recipient derived a real benefit, and that there is no duplication. Weak documentation is often decisive here.

b) Cost base and allocation keys

Taxpayers must also justify the nature and amount of the costs incurred, their direct link to the services provided, and the objectivity of the allocation criteria used. Allocation mechanisms that are opaque or overly generic are frequently challenged.

c) Pricing

For low value-adding services, the OECD Guidelines allow for a simplified approach using a standard markup. For more complex or strategic services, pricing must be supported either by reliable comparables or by a sound economic analysis in line with the arm’s length principle.

3. Intragroup financing

Related-party financing is another frequent source of controversy.

a) Contractual terms and actual conduct

Failure to comply with agreed loan terms—such as repayment schedules, guarantees, or interest rates—can lead the Tax Agency to challenge the substance of the transaction itself.

b) Debt capacity

If the borrower would not have been able to secure financing on similar terms from an independent lender, the transaction may be recharacterized as a capital contribution, an equity instrument, or, in some cases, a donation. Demonstrating repayment capacity and a clear business rationale is therefore essential.

c) Cash pooling arrangements

In cash pooling structures, the focus is on whether interest rates are appropriate, functions and risks are properly delineated, and the pool leader is adequately—but not excessively—remunerated. Recent Supreme Court case law makes it clear that a pool leader performing mainly coordination tasks should not earn a disproportionate return.

4. Shareholder–company dealings

Certain shareholder–company transactions are particularly sensitive.

a) Use of company assets

When shareholders use company assets free of charge, adjustments may be made under related-party rules. If the asset was acquired solely for personal use, taxation often falls under the rules on benefits in kind. Recent administrative guidance has addressed how these situations should be treated from both a primary and secondary adjustment perspective.

b) Multi-entity structures

Structures involving an operating company, a service-providing holding company, and an individual shareholder can be especially complex. Where the intermediary entity adds little value, the authorities have supported a cost-plus approach and the allocation of most profits to the individual.

c) Directors’ remuneration

While directors’ fees are not easily comparable, remuneration may still be reviewed under the arm’s length principle when services are provided through a corporate director. Even in the absence of direct comparables, the Tax Agency may assess whether the agreed remuneration makes economic sense.

5. Restructurings and intangibles

Business restructurings and transactions involving intangible assets are among the most technically complex areas. Here, a thorough functional analysis, clear risk allocation, and a proper understanding of where value is created are critical.

Rising litigation in related-party matters reflects not just formal shortcomings, but a growing focus on whether group structures make economic sense. Strong documentation, alignment between legal form and actual conduct, and early risk assessment are now central to an effective tax compliance strategy.

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