Hi gilkelly,
Inheritance tax is not covered by the double taxation agreement. As you and your brothers are the beneficial owners of the property, each of you will need to report the disposal in a self assessment tax return, with all figures in pounds sterling. The acquisition and disposal costs such as solicitors fees, estate agent fees, should be split between each of the brothers, according to their percentage of ownership. The same can be said for the Irish Capital Gains tax paid.
Under the terms of Self Assessment, we do not provide an official exchange rate and the onus is on the individual to use a just and reasonable exchange rate for each acquisition and disposal. For your convenience, there are exchange rates at:
UK Government Web Archive/ukgwa/20231016190054/
Exchange rates from HMRC in CSV and XML format and for older rates at:
UK Government Web Archive/ ukgwa/20100202113554/
Exchange rates from HMRC in CSV and XML format.
You are free to use any of the supplied rates or one of your own choosing.
Thank you.