While communicating with business people, the language you use must be consistently appropriate in style and tone.
The following are the basic features of formal writing.
Write all verbs in full. Do not use contracted forms like don’t or can’t.
Do not use abbreviations such as info (for information) and asap (for as soon as possible).
Limit the use of passive voice. However, there are some situations where passive verb forms are preferred to active forms. For example, active verb forms used with the first person singular are not considered appropriate in formal or academic writing. Write ‘A copy of the document will be mailed to you as soon as possible’ instead of ‘I will mail you a copy of the document asap’.
Watch your vocabulary. Certain words are considered informal. Examples are: fix, begin, start, OK, thanks etc. Avoid them in formal writing. Instead use words like repair (for fix), commence (for start / begin), in order / all right (for OK) and thank you (for thanks).
Avoid informal intensifiers like really and so. Instead use more sophisticated ones such as extremely, highly, entirely etc.
Limit the use of phrasal verbs. As far as possible avoid using them, but if that is not possible limit their use. It is usually possible to express the same idea using standard verb forms.
Certain discourse markers are considered informal. Avoid using them. For example, write incidentally instead of by the way.
Do not leave out words. Ellipsis is not acceptable in formal writing. Write ‘I hope to see you soon’ instead of ‘Hope to see you soon.’