An employee appreciation or thank you letter is a formal message from an employer that recognizes the former's contribution to the company they work for. A simple yet powerful tool, these letters can express gratitude, boost morale, and improve job satisfaction.Commonwealth Employee Certificate of Achievement. Nominate a co-worker for their extraordinary contributions to public service. Guidelines for writing appreciation letters: State what you appreciate and briefly explain why. In recognition of this outstanding performance, you have been named the winner of the Above and Beyond Award for this quarter. You've been working so hard towards completing this project, and it hasn't gone unnoticed! Heartiest congratulations on your phenomenal work. Learn how to write an employee appreciation letter with these templates and examples. Download the template for free (PDF or Word).