The general rule is that you pay social security contributions in the country in which you work. The Agreement states, however, that if you are employed or self-employed in both countries, you pay contributions only in the country in which you reside.
If you are sent by your Irish employer, whose main place of business is in Ireland, to the Isle of Man or the Channel Islands for a temporary period, you may continue to pay Irish social insurance contributions for the first 3 years of the assignment. This applies whether you continue to work directly for your Irish employer or for a subsidiary or affiliated company. If the assignment exceeds 3 years, you may be able to continue to pay Irish social security contributions but only in exceptional circumstances and with agreement from both the UK and Irish authorities.
Similarly, if a person is sent on temporary assignment by an Isle of Man or Channel Islands employer to work in Ireland, they will continue to pay only the relevant UK contributions for the first 3 years. If the assignment exceeds 3 years, the person may continue to pay UK contributions in exceptional circumstances and with agreement from both the UK and Irish authorites.
If you would like further information, see Section 10 for contact details.