A founding document turned into English
British offices read company paperwork in English, so a foreign founding document has to arrive in English to be any use. An official translation of an Articles of Incorporation in Sheffield is written from a scan and comes back signed and dated. Your document is not sent anywhere and not marked in any way; the English pages are an addition, meant to be read next to it.
Identifiers are not words
Two kinds of thing sit on a founding document. There are words that carry meaning, such as what the company may do and how it takes decisions, and those are written out in English. Then there are identifiers: the registered name, the registration number, the date of formation, the address on the register. Those are handles, and a handle only works if it stays the same shape.
Change one and you break the link to the register that holds the entry. A reader who cannot look the company up is left with a description of a business rather than proof that it exists. So a certified translation of an Articles of Incorporation in United Kingdom reproduces every identifier character for character, and does the explaining around them instead.
Who signs, and what to have ready
The pages are signed by a certified translator holding an ITI or CIOL qualification, and the signed statement says that the English matches the document it was made from. Have the whole constitution to hand before you start, including any later amendments, because a company's rules are often changed after formation and a British reader will want the current picture rather than the first one.
One local note. Sheffield Register Office at Town Hall, Pinstone Street, Sheffield S1 2HH issues certified copies of birth, marriage and death records, and a company's founding paper is not among them. A fresh copy of that comes from the register the company sits on in its own country, so allow for the wait if the copy you hold is worn or incomplete.
Cost and turnaround
The rate is £25 a page, counted from the scan up front, and standard work runs 2–3 business days with express at 24 hours. Company constitutions tend to run long, so the count is worth settling before you commit to a deadline. Sending the amendments in the same batch keeps the whole set on one clock instead of two.