Whenever possible, use common words. Words that nearly every adult is likely to understand. Words that don't require a trip to the dictionary.
Your aim in all business and professional writing is to get your message across quickly and clearly. Using common words is a plain language trick that really helps. It's a simple way to spruce up your writing, making it more concise and more readable.
You'll find hundreds of examples, once you start looking. Here are a few for starters:
Experiment. Wouldn't your writing be clearer if you used:
200 examples of unnecessarily complicated words, and alternatives, were published by the Local Government Association (UK) in March 2009.