Is it necessary to send a thank you note in response to a thank you note?

It is not necessary to send a thank you note in response to a thank you note. However, it is polite to do so.

People who receive a thank you note from a client or business associate may wish to respond to build a stronger relationship with them. The note should remain concise, and it should state that they appreciate the sender's custom.

For example, "We would like to thank you for your custom and your kind words. We appreciate all of our customers and look forward to building our relationship with you. We look forward to you using our services/products again." This is a good way to reach out to someone who appreciates a business while encouraging future interactions.