Updates to the road transport price adjustment mechanism in Spain: impact of RDL 7/2026 and 9/2026

Following its meeting with the National Road Transport Committee (CNTC), the Spanish Ministry of Transport and Sustainable Mobility has announced a set of measures governing the adjustment of transport prices in line with fluctuations in fuel costs. These developments arise primarily from Royal Decree-Law 7/2026 of 20 March and Royal Decree-Law 9/2026 of 14 April, which introduce significant changes to the price adjustment system.

Changes introduced by Royal Decree-Law 7/2026

Temporary tax measures affecting hydrocarbons and VAT have led to technical adjustments in the calculation mechanism:

• New reference – pre-tax price (PTP): while the exceptional tax measures remain in force, the diesel price used to calculate variable G must be determined on a pre-tax basis. This ensures that tax changes do not distort the transport price adjustment mechanism.
• Exclusion of subsidies: extraordinary public aid (such as the €0.20 per litre rebate or similar measures) is excluded from the adjustment formula. These measures are granted exclusively to carriers and do not affect the reference price.
• Application of the formula at a 5% threshold: the mandatory application of the formula set out in Order FOM/1882/2012 is maintained where fuel price variation reaches 5% compared to the time the contract was entered into, although a lower threshold may be agreed in writing.

Key developments under Royal Decree-Law 9/2026

This regulation significantly strengthens the mandatory nature of the transport price adjustment system, aiming to improve transparency and contractual balance.

Mandatory nature and transparency

• Price adjustment based on fuel costs is now mandatory in all cases.
• It applies to both increases and decreases in price.
• It must always be itemised separately on the invoice, ensuring full traceability of the adjustment.

Automatic application

• The adjustment applies automatically when fuel price variation reaches 5%, unless a lower threshold has been expressly agreed.
• In contracts of successive performance:
  • the adjustment must be carried out in each agreed billing period; and
  • in all cases, and on an automatic basis, the initially agreed price must be adjusted in each period by applying the formula set out in Order FOM/1882/2012 (clause 3.4), irrespective of the percentage variation in fuel prices.

Additionally, any contractual clause that limits or excludes this adjustment mechanism is expressly declared null and void.

Price adjustment calculation mechanism

The new framework adapts the formula to reflect current conditions in the diesel market, incorporating the following elements:

• ΔP: variation in the transport price.
• G: percentage variation in the average weekly diesel price between the time the contract is entered into and the performance of the transport service, as published by the competent authorities.
• P: initial transport price.
• C: coefficient linked to the pre-tax diesel price.

The adjustment is calculated using the following formula:

ΔP = (G × P × C) / 100

where ΔP represents the variation in the agreed transport price.

Calculation of index G

• For vehicles eligible for hydrocarbon tax refunds: the fuel purchase price is used, excluding VAT and disregarding any partial refund applicable to professional diesel.
• For vehicles not eligible for such refunds: the fuel purchase price is used, excluding VAT.

Coefficient C

Coefficient C varies depending on the type of vehicle, reflecting the relative weight of fuel costs in overall operating expenses, as follows:

• vehicles ≥ 20,000 kg (excluding construction vehicles);
• vehicles between 3,500 kg and 20,000 kg (excluding construction vehicles);
• construction vehicles > 3,500 kg;
• vehicles ≤ 3,500 kg.

Practical application (operational steps)

In practice, the mechanism operates as follows.

First, the relevant reference points must be identified: the time at which the contract was entered into (reference week) and the time at which the transport service is performed. In contracts of successive performance, this analysis must be carried out for each billing period, in accordance with the temporal criteria consistently applied within the contractual relationship.

Next, the average weekly diesel price corresponding to each of these points is determined, and the percentage variation between them (G) is calculated.

On that basis, it must be assessed whether the applicable threshold has been exceeded. If the variation reaches 5% compared to the time the contract was entered into (or a lower threshold agreed in writing), the price adjustment applies; otherwise, no adjustment is made. This same approach applies to contracts of successive performance, with the assessment carried out in each billing period.

Where the adjustment applies, it is calculated on the basis of the initial transport price (P), applying the variation obtained and weighting it by the coefficient corresponding to the type of vehicle (C). The resulting amount must be reflected on the invoice as a separate line item, either increasing or decreasing the transport price.

The assessment is always based on a comparison between two points in time (contract formation and performance, or the relevant billing period), which determines the variation in fuel prices. Once the applicable threshold has been exceeded, the adjustment is incorporated into the transport price in accordance with the variables described above. This process is repeated in each billing period in the case of contracts of an ongoing nature.

Treatment of fuel subsidies

The principle already established under Royal Decree-Law 7/2026 is reinforced:

• until 30 June 2026, diesel rebates may not be included in the calculation of the price adjustment; and
• their exclusive nature for the benefit of the carrier is expressly recognised.

Penalty regime

Royal Decree-Law 9/2026 introduces a significant strengthening of administrative oversight:

• it constitutes an infringement for the shipper or the party responsible for payment to prevent or refuse the itemisation of the fuel-related price adjustment on the invoice, particularly in respect of services exceeding €3,000.

For an infringement to be established, the carrier must demonstrate:

• that a properly itemised invoice was issued and subsequently rejected or altered; or
• that it was not possible to issue the invoice correctly or to secure its acceptance in the required form.

Sanctions

• Fines may reach up to €6,000, depending on the value of the transport service.
• In aggravated or repeat cases, fines may increase to €18,000, or up to €30,000 in the most serious cases.

Practical guidance

Compliance

For compliance purposes, it is essential that the invoice includes the fuel-related price adjustment as a clearly identifiable and separately itemised component, linked to the relevant service or billing period.

Full traceability of the calculation must also be ensured, including the time of contract formation, the time of performance, the variation applied, and the coefficient used. In addition, any evidence of invoice rejection or modification must be retained, in order to demonstrate the proper application of the mechanism in the event of review or dispute.

Contractual considerations

From a contractual perspective, it is necessary to ensure that:

• no clauses limit or exclude the price adjustment mechanism;
• the applicable threshold is clearly defined; and
• in contracts of successive performance, the temporal reference used for calculating fuel prices is properly aligned with the billing period.

Correct identification of the vehicle type is also essential, as it directly determines the applicable coefficient.

Invoicing requirements

In invoicing, the transport price must be shown separately from the fuel-related adjustment. The latter must appear as an independent line item, clearly identifying the relevant service or period and allowing it to be reconciled with the underlying calculation.

Conclusion

Both regulations consolidate a mandatory, objective and automatic price adjustment mechanism linked to fuel costs. They reinforce transparency in invoicing while significantly restricting party autonomy in this area.

This represents a substantial step forward in safeguarding the economic balance of the road transport sector, with important practical implications for both carriers and consignors.