There are 2 options for assigning invoice numbers when you create invoices (one time or recurring). You can allow QuickBooks to assign the number or you can have Recur360 assign it.
If you are using QuickBooks Desktop and allow QuickBooks to assign the invoice number it will be assigned and written back to Recur360 on the sync after the invoice is created. If you choose this we recommend that you also enable the setting to not email the invoice until after the invoice number is assigned, that way the invoice email will include the invoice number. Go to Settings - Email and select this option:
Note: If you check this option it can delay customers receiving emails since they will not send until a sync is completed. So, if invoices are created on a Friday, but a sync is not completed until Monday the emails will be sent to customers on Monday.
With QuickBooks Online invoice numbers are assigned as soon as the invoice is created, since it syncs over immediately. However with QuickBooks online there is an option to enable "Custom Transaction Numbers". If this is set to yes then QuickBooks does not assign invoice numbers and they will be blank.
To resolve this turn off Custom Transaction Numbers in QuickBooks Online. Here is a link to an article to change that setting: https://recur360.kb.help/custom-transaction-numbers-in-QuickBooks-online/
Another option is to allow Recur360 to assign the invoice numbers. Then an invoice number is assigned immediately and Recur360 pushes that invoice number into QuickBooks. In Settings - Account on the right side of the screen in the Invoice Settings section is an option to have Recur360 generate invoice numbers.
Check the box and assign the next invoice number. You can also assign a prefix to append in front of the invoice number.
When you save it will show what the next invoice number will be.
You can change the next number by selecting the Override Invoice Starting Number.