In which language must a COC document be?

In which language must a COC document be?
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In which national language must the COC (Certificate of Conformity) be written?

Sporadically we are asked to issue the EC Certificate of Conformity (COC) for a specific vehicle in a language other than German. Many of our customers from Italy, France or England are uncertain whether the document we provide in German will be accepted by the local authorities. Thereby, EU Regulation 2018/858 Chapter IV Article 36(5) states that "The Certificate of Conformity in paper form shall be drawn up in at least one of the official languages of the Union."
This means a Certificate of Conformity (COC) must be issued in one of the official languages of the European Union, which includes all 24 official languages of the EU. As long as the document is written in Bulgarian, Croatian, Czech, Danish, Dutch, English, Estonian, Finnish, French, German, Greek, Hungarian, Irish, Italian, Latvian, Lithuanian, Maltese, Polish, Portuguese, Romanian, Slovakian, Slovenian, Spanish or Swedish, local authorities are obliged to accept it.
Also in countries such as the UK or Switzerland, the COC in the official EU languages is currently accepted.
One may grumble about the EU and its slow mills, but the advantages of this union have to be acknowledged...