Revenue has issued a tax bill of €1.6b to a major pharmaceutical company.
The assessment is the second largest in Irish history after Apple was ordered to pay €13bn in 2016.
The tax bill served on Dublin-based pharma company Perrigo relates to Elan, a company that was bought by Perrigo five years ago.
Elan sold its interests in a multiple sclerosis drug in 2013 to a company called Biogen for an up-front payment of $3.25bn and a share of future royalties.
According to the Irish Times, the company said that taxes were paid on the profits from the transaction at the corporation tax rate of 12.5%.
However, Revenue argues that Elan was liable at the capital gains tax rate of 33%.
Perrigo has said it disagrees with Revenue and intends to contest the bill.