Thank you for joining the Community. I'd be happy to help share some information about the resale number in QuickBooks Desktop.
When you enter a resale number in the customer's profile, it will not reflect on the transactions automatically. It'll only show once you add a custom field to your invoice template.
To ensure that I'm on the same page, may I ask where in QuickBooks that the 2019 resale number is changing the last year's number? Any other details would be helpful too for me to better assist you.
Feel free to hit Reply below if you're referring to something else, or if you have any other questions about QuickBooks. I'll be happy to help you out.