DT9863 - Double Taxation Relief Manual: Guidance by country: Ireland: completion of forms
Assistance in the completion of the claim forms referred to in DT9861 can be given on request by tax offices, but the UK Inspector’s official functions in relation to Irish tax are limited to certifying residence, etc. in the United Kingdom and the UK Inspector cannot speak with authority about Irish tax.
The determination of the claim rests solely with the Irish authorities.