Two-time world champion Max Verstappen's Red Bull Formula One team exceeded the budget cap for the 2021 season, the International Automobile Federation (FIA) said on Monday, adding that the offence was a "minor violation".
Aston Martin was also found in breach of Formula 1 financial rules, the FIA announced, adding that any punishment would be decided at a later date.
"We note the findings by the FIA of 'minor overspend breaches'... with surprise and disappointment," tweeted Red Bull.
The cap came into effect last season and was set at 145 million dollars (currently 149.6 million euros). It is intended to limit spending to make the sport viable and also to close the competitive gap between big and small teams. Mercedes, Ferrari and Red Bull were particularly affected.
Even so, Verstappen ended the season by edging Lewis Hamilton of Mercedes to win a first world title.
The FIA said it was "currently determining the appropriate course of action to be taken".
A "minor overspend breach", the statement said, is less than five percent of a team's total cap and can "result in financial penalties and/or minor sporting penalties."
Red Bull insisted on Twitter that they had not broken the rules.
"We need to carefully review the FIA's findings as our belief remains that the relevant costs are under the 2021 cost cap amount."
The FIA said its 'Cost Cap Administration' had finished a review of the financial documentation submitted by each team for 2021 and "issued certificates of compliance to seven of the 10".
The third exception was Williams, where there had been a problem with "a previous procedural breach" which the team had "remediated" in a "timely, cooperative and transparent manner".
The statement stressed that because the season under review was the first with a cost cap, the FIA had limited itself "to reviewing the submissions made by the competitors and that no full formal investigations were launched."
The statement said that the first option for the Cost Cap Administration was to agree a settlement with the team involved.
If the two sides are unable to reach an agreement, or if the team is not in favour of seeking an agreement, it can refer the dispute to a panel of six to 12 judges elected by the FIA general assembly.
"Despite all the conjecture and positioning of others, there is of course a process under the regulations with the FIA which we will respectfully follow while we consider all the options available to us," said Red Bull.
The statement added that "the regulations are highly complex, reflecting the complexity of the sport as a whole".
It also said that all the teams "acted at all times in a spirit of good faith and cooperation throughout the process".
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