You should get a warning if a duplicate bill number is entered. This used to be standard in MYOB and is essential to all business.

Hi karen6305,  
 
Thanks for your post. I would like to extend to you a warm welcome to the Community Forum.

Your suggestions and feedback are important to us, and we appreciate you taking the time to share them with us. We understand the importance of having a warning for duplicate bill numbers in your business, and we will make sure that your requests and feedback will be effectively communicated to the team. 
 
 
Please do not hesitate to post again if you need help in the future.  
 
Cheers,   
Leneth