Most Americans and Britons understand each other, and understand most technical and legal texts written for readers in either country. However, some engineering words are different, especially car parts (bonnet (UK)=hood (US)).

Legal and financial texts, however, require special attention. Despite both countries having legal systems based on common law, rather than Roman law like most of the rest of the world, the UK has no supreme court, and different court levels. In addition, legal language reforms were passed in 1999 in the UK, requiring that simpler language be used in legal documents. The accounting systems of the two countries are also different.

Any text that is intended for marketing should be translated or edited by a native speaker of the target language to ensure that no unexpected meaning is introduced.

Make sure you know which dialect you need.