Dear …
The end of another tax season is __(fast approaching/now at hand/etc.)__ and we want to thank you for choosing __(Name of Accounting Firm)__ as your tax accounting firm __(again)__ this year. We appreciate your support and the confidence that you have placed in us to advise you regarding your accounting and tax issues. It was our pleasure to be of service to you.
Our commitment to our clients is to ensure that they receive the best in professional accounting services by knowledgeable staff. We hope that you have experienced that with us and will continue to choose __(Name of Accounting Firm)__ for your accounting needs. Please feel free to contact us anytime with any special needs or accounting questions.
Again, thank you, __(Name)__. We are looking forward to the privilege to serving you again.
Sincerely,