What constitutes a dialect and what to do about it is one of the most misunderstood concepts in translation, perhaps second only to the "native speaker" syndrome (the pernicious idea, promoted by some language schools, that being a native speaker qualifies a person to translate).

Every major language has regional and class variations, but more importantly, every language also has clear standards and guidelines for correct and incorrect grammar and usage.

Although there may be times when it is appropriate to write in a regional or class dialect (targeted advertising comes to mind), business communications (and this includes technical writings, contracts, legislation, financial statements, etc.) must always be written in standard language.