Apostille vs. Embassy legalisation for Bulgaria
An apostille is the accepted way to certify papers from the UK for use in Bulgaria. This simplifies matters, as you will not have to visit the Bulgarian Embassy or get any other stamp from them. The Legalisation Office adds the apostille after they have checked the signature on the paper. Once it is there, it counts as valid proof in any office in Bulgaria.
Bulgaria's Hague status & what it means
Bulgaria has been part of the Apostille Convention since 2001. This agreement among countries allows the use of apostilles in place of longer embassy legalisation chains. Your paper only needs one extra page, the apostille itself, which the FCDO attaches. It means the end office in Bulgaria can look up this seal in an international register to confirm it is real.
The Cardiff → Bulgaria route step by step
The process for an apostille from United Kingdom to Bulgaria starts by making sure you have the right version of the paper. If you have a certificate like a birth or marriage record from Cardiff Register Office at City Hall, you can get a fresh certified copy made there rather than risk your original in the post. The clerk will print and stamp it as a true copy, which the Legalisation Office can then look at. This keeps the file you care about safe at home while the office works on the new one.
Once you have the right copy or the original from a public body, package it with the fee and a cover note listing your contact details and where in Bulgaria it will be used. The Legalisation Office has to see the actual signature of the official who signed your paper to know it is genuine. After they attach the apostille, the bundle is legal for use anywhere in Bulgaria.
Bulgarian rules for UK documents
Normally, you also need to prepare a document legalisation for Bulgaria with both the apostille and a translation. Bulgarian authorities will request a court-approved version from a sworn translator who knows both languages. The translator works from a copy of your apostilled paper, not the original one, so you can keep that safe. They will produce a separate set of pages in Bulgarian that reference the official stamp they saw.
What you need for an apostille for Bulgaria
You must send the paper or a fresh certified copy to The Legalisation Office by post. There is no public counter for walk-ins, so allow working days for the post each way. Some papers need an additional certificate from the body that first issued them before the Legalisation Office will take them, but this depends on what the paper is. The FCDO keeps a register of recognised UK authorities and will check which one signed yours.