Look up per diem reimbursement rates and mileage deductions for business travel worldwide.

Complete
Ireland → Saint Helena, SH
Item Name Destination Amount Conditions
Incidentals Ascension Island 10 EUR per day Actual-cost destination (Note 1, Circular 07/2017): the overnight rate is the vouched cost of accommodation and three meals, the ten-hour rate is the vouched cost of two meals and the five-hour rate is the vouched cost of one meal, in each case plus this incidental expenses allowance of EUR 10 per day.
Incidentals Tristan Da Cunha 10 EUR per day Actual-cost destination (Note 1, Circular 07/2017): the overnight rate is the vouched cost of accommodation and three meals, the ten-hour rate is the vouched cost of two meals and the five-hour rate is the vouched cost of one meal, in each case plus this incidental expenses allowance of EUR 10 per day.

Source URL:
https://www.revenue.ie/en/employing-people/documents/dper-circular-07-2017-subsistence-allowances-abroad.pdf
This source provides official travel rate information from revenue.ie.