Answer
The acquirer of the equity instrument is subject to Irish stamp duty. Irish stamp duty is automatically withheld and DEGIRO passes this tax charge on to its clients.
IE Stamp Duty generally applies to shares or similar instruments issued by Irish companies listed on the Irish Stock Exchange. Small and medium sized companies listed on Euronext Growth (formerly the Enterprise Securities Market) of the Irish Stock Exchange are exempted from IE Stamp Duty. The taxable event is the purchase transaction.
The tax rate is 1.00% (as of 2020) of the transaction value.