Why has QB all of a sudden started sending 4 emails when I go into an invoice and tell it to send a reminder and how can I make it stop?

Hi there marci-cccinc-ca,

It's important that all your transactions are correctly entered for your sales totals to be accurate. QuickBooks Online is a great tool able to help you create and send invoices for your customers. I can point you in the right direction for assistance with reminders. 

if your invoice reminders are sent multiple multiple times after asking to send it once, I recommend reaching out to the QuickBooks Online support team outside of the Community. They'll be able to view this with you in a secure setting to provide troubleshooting to get the error with sending reminders resolved, as well as collect the required information to notify the engineers if the error still persists. You can reach them using these methods:

Schedule a Callback or start a Chat: click (?)Help in the upper right > type and enter "Contact support" into the QB Assistant > click Contact Us > explain your situation > click Let's Talk > choose Get a callback or Start a Chat.
Social Media: Facebook and X / Twitter 

If you have any other questions, feel free to reach out here.