Japan works in Japanese
Offices in Japan handle their paperwork in Japanese, and a British certificate is a foreign object to them until a Japanese version arrives with it. A certified translation into Japanese in Birmingham supplies that version. Your English sheet is not marked, kept or altered at any point in the work.
What makes this route demanding is not the sentences but the decisions around them. Japanese uses several writing systems side by side, and the choice of which one a name or a place belongs in is a judgement a certified translator makes deliberately, document by document.
Names, dates and numbers
The three things that get a file returned are a name written two ways, a date silently converted, and a reference number tidied up. All three are avoidable. The method is to fix each one once, against whatever Japanese record you already hold, and then repeat that exact form on every sheet in the bundle.
So the useful thing you can do before ordering is dig out any Japanese paperwork in your possession — an older visa, a residence card, a previous translation. An official Japanese translation in Birmingham built to agree with those documents saves a round of questions later.
The signature, the cost and the clock
Beneath the Japanese sits a certificate of accuracy: the translator's name, the date, and a plain statement that the meaning was carried across whole. That signed block is what turns a certified translation for Japan into something an office will file rather than merely read, because a named person now stands behind every line.
Budget about £25 a page and count sides rather than documents. Standard delivery is 3–5 business days from complete scans, with 48 hours available in express where a date is already fixed. Sending the whole bundle at once keeps the name and place forms consistent from the first page to the last.