Kingspan, the Irish building materials firm, has been fined €40m (£33.9m) by the European Commission for providing it with incorrect and misleading information during a competition investigation.
In 2021 Kingspan planned to take over Trimo, a rival manufacturer of insulating panels.
That required an investigation under European Union (EU) merger rules to make sure it would not lead to significantly reduced competition. The commission has concluded that Kingspan gave misleading information during that process.
In a statement, Kingspan said it noted the decision and would appeal it "in full".
In 2022 Kingspan said it would not pursue the deal with Trimo after the watchdog said it could lead to higher prices.
The commission then opened an investigation to examine whether Kingspan had provided incorrect and misleading information.
An interim conclusion said Kingspan had broken the rules on six separate grounds with Thursday's final judgement reducing that to four breaches.
It was fined €10m (£8.5m) for each breach.
'No compromise on disclosure'
It found that Kingspan had asserted the non-existence of key documents, misrepresented facts, or claimed it was impossible to provide key information that only the company was in a position to provide.
"When companies withhold or distort the truth, they undermine a system that protects fair competition for everyone," the competition commissioner Teresa Ribera said.
"There can be no compromise on disclosure and transparency. If they fail to do so, we do and will act firmly."
Kingspan, which is based in County Cavan, is one of Ireland's largest businesses.
It made a pre-tax profit of just over €850m (£720m) in 2025 and is currently valued at around €18bn (£15.3bn).