The Dreaded Comma Splice
Many businesspeople today are in the habit of combining two independent clauses with just a comma, like this:
Revenues were plummeting, we decided to close two branches.
Unfortunately, the sentence above is actually a sentence error called a comma splice. If you are writing a creative piece — a poem or novel, for example — you may occasionally find stylistic reasons to use a comma splice. Business writing, however, is a place for traditional punctuation, not experimentation. Think of the comma as being too frail, too delicate a piece of punctuation to hold apart two independent clauses without the additional help of some kind of combining word.
Remember: in business writing, where you can put a period you can virtually never put a comma. If you do, you will in most cases create a comma splice. Periods and commas are like punctuation enemies; though they may be distant relatives, they do not get along and do not hang out in the same kinds of places.