A sworn translation is always necessary for official documents intended to be in a court of law or for official purposes. An affidavit is a statement in which it is testified that the attached translation is a true and accurate translation of the original document, this being sworn in front of a qualified solicitor.
A notarized translation (also known as notarisation of a translation) is often required for official documents and is more formal than a certified translation. Once the translation has been completed, it will then be declared on oath and in writing before a Notary Public that the translated document is a true and accurate translation of the original document. The Notary will then sign and stamp the certifying letter with their embossed seal and signature and add the date. This will be attached to the document to acknowledge that it is genuine. This is often requested for use abroad or for translations required for financial matters, such as when applying for a mortgage or opening a bank account.