As a freelance translator I regularly get the question to translate into Flemish. I notice from reactions and questions from clients that it is not always clear how to make a difference between the language from Dutch speaking persons in the Netherlands and the language from Dutch speaking persons in Belgium. On top of that there is the term in Spanish ‘holandés’ for Dutch while there is also ‘neerlandés’ and ‘flamenco’. The easiest way to get over this confusion is to use the shorter versions of the languages as indicated in many CAT-tools: NL-NL and NL-BE.
In fact it can be perfectly compared with the situation of English (EN) and Spanish (ES) where different versions exist, for e.g. Spanish from Mexico and English from Australia. Even in French there are different versions like FR-BE, FR-CH, FR-CA, FR-LU and FR-FR (Belgium, Switzerland, Canada, Luxembourg, France).
The way I deal with this is checking .be or .nl websites and references like www.vandale.nl, taaladvies.net and www.schrijfwijzer.nl to see if a certain word where I have doubts is specifically mentioned as ‘Belgisch-Nederlands’ or ‘Vlaams’ (Flemish).
Recently the Belgium newspaper in Dutch ‘De Standaard’ published a small list of 1000 words that are typical Dutch from the Netherlands with the title ‘Hoe Vlaams mag uw Nederlands zijn?’ (To what extent your Flemish is acceptable as Dutch?). Another good resource to find out what is acceptable and what isn’t.