Here is a topic that comes up often:
Do we capitalize department, as in “Finance Department”? And how about department by itself?
These sentences illustrate standard capitalization of words such as department, committee, team, unit, lab, division, and company:
Jamie works in the Finance Department. (Finance is the name of a department. Both words are capitalized.)
Jamie works in Finance. (Finance is the name of the department, group, or division.)
Jamie works in finance. (Finance is Jamie’s specialty but not the name of his or her team.)
Have some finance people review this budget. (Finance refers to an area of expertise–not a specific group.)
Jamie is joining the department. (Department, group, company, and similar words are lowercase without a specific name, but see below.)
Typically the word Company or Division, standing alone, is capitalized in legal documents when it stands for the company’s or division’s name.
The title of this post is “Sales Department or sales department?” When you write to a company and want to communicate with someone in sales or about sales, the correct rendering is lowercase. Capitalize Sales (and any similar word) only when you know it is the name of the unit. Often departments have numbers or additional letters in their titles as well, here is a piece I wrote on how to handle capitalization of words followed by numbers or letters.
If the word in question is describing a field of expertise, then the word is not capitalized, for example: “Greg has a background in accounting”. If the word is describing a specific department within an organization, then the word is capitalized: “Greg is the head of Accounting at Michelin Tires”.