A document written to order
Most papers that get certified are records. An entry already exists somewhere, and the sheet in your hand is a copy of it, faithful to whatever was written down at the time. A banking letter works the other way round: it is composed when somebody asks for it, so its contents are still open at the moment of the request and closed the moment it is printed.
That difference is worth using while it lasts. The names, the dates and the way the account is described can all be lined up with the passport, the application or the file the letter supports, before a single mark sits on the page. No later stage of the process offers that chance again, because every later stage takes the sheet as it finds it.
One certifying office, wherever the letter was written
Anyone setting out to apostille a Bank Reference Letter in the United Kingdom deals with a single certifying office rather than several. The Legalisation Office (Foreign, Commonwealth & Development Office) covers the whole country and works by post from PO Box 6255, Milton Keynes MK10 1XX. The same office also issues UK e-Apostilles, so the certificate is not always a paper attachment.
The Belfast end of the job is therefore the letter itself, not a counter to find. The General Register Office for Northern Ireland (GRONI) at Colby House, Stranmillis Court, Belfast BT9 5RR issues certified copies of birth, marriage and death entries registered here, and that list is worth knowing precisely because a banking letter falls outside it and comes from the bank that holds the account.
What the certification stage charges
The published fee is £45 per document by standard post, or £40 per document next-day where the sender is a registered business. The unit is the document, so a letter needed by two different recipients is two letters and two charges. There is no bundle rate that makes the second sheet cheaper than the first, and the count is taken from the paperwork rather than the envelope.
No turnaround figure is published for this route, and putting one here would be a guess dressed up as guidance. What can be said is that the office works through the mail in both directions, so a realistic calendar holds two postal legs as well as the handling time in between. Files planned with that in mind rarely turn into urgent ones.
Why the letter is being certified at all
People usually reach this stage because an office in another country has asked to see proof of a banking relationship and will only take it with a certificate attached. On its own the letter is a private document written by one company about one customer. The apostille is what lets a reader abroad treat the signature on it as one a British authority has placed and can account for.
That also sets a limit worth understanding. The certificate speaks to the signature and seal on the page and to nothing beyond them. It does not confirm a balance, a standing or any other statement the letter makes. Whoever reads the letter abroad still weighs its contents in the ordinary way; the mark only removes the question of where the sheet came from.
Acceptance, and what the destination decides
Whether this certificate finishes the job depends on the country the letter is bound for. Some read the apostille on sight and add nothing to it. Others keep a further consular stage afterwards, and there the British mark is the opening move. The fixed half of the errand is the one described on this page; the variable half belongs to the destination.
Translation is a separate matter from certification, and the two are often run together in people's minds. The apostille attaches to the sheet as written and does not turn the letter into another language, nor does it travel differently when a translation is supplied alongside. Where a destination wants the text in its own language, that work sits beside the certificate rather than in place of it.