The language Oman requires
A certified translation into Arabic is required for documents used in Oman, so an English record from Northern Ireland needs an Arabic version filed with it. Only the translation is certified. The English sheet keeps the form it was issued in, nothing is added to it, and it does not have to leave your hands for the Arabic to be produced.
An errand with no counter
People picture this as a trip into town and then discover there is nowhere to go. The register works by post. The writing happens on scans. The finished set comes back as signed pages you print or forward. No part of the chain has an appointment or a queue, so what you are planning is postal time, never travel time.
What that means for the calendar
Because no leg of the job needs you present, none of it is bounded by opening hours or by how far Colby House sits from your front door. What bounds it is the post and the length of the bundle. A certified translation in Belfast for Oman is therefore planned in days of postal time and days of writing time, and turning up somewhere shortens neither.
Where the Belfast record is issued
Northern Ireland administers its own civil registration, so a birth, marriage or death registered in Belfast comes from the General Register Office for Northern Ireland (GRONI) at Colby House, Stranmillis Court, Belfast BT9 5RR and not from a registry in Great Britain. That office deals in post rather than in personal callers, and a copy ordered from it is a full record you can put in front of the translator in place of your own.
Cost and pace
The rate is about £25 for each page as issued, and a certified translation for Oman is counted in sides rather than in documents. Standard production is 3–5 business days once legible scans exist, and a 48-hour route is there for a close date. Neither number depends on where you are standing, which is the practical upshot of an errand that never asks you to be anywhere.