Many people have Custom Transaction Numbers enabled in QuickBooks Online without realizing it. With Custom Transaction Numbers enabled, QuickBooks Online will not provide Invoice numbers when you create an Invoice through Breadwinner (or any other QuickBooks Online Integration).
Please note, there is a different setting in QuickBooks Online for Custom Transaction Numbers for Purchase Orders. If you are using Purchase Orders, please see the last section in this article.
Custom Transction Numbers for Invoices
If you have Custom Transaction Numbers enabled, when you create your Invoice using Breadwinner you will have the option to provide an Invoice Number just before Invoice creation. Please be aware that QuickBooks Online will reject duplicate numbers but will accept blank numbers.
Additionally, if you want to populate this Custom Transaction Number / Invoice Number from a custom field on your Opportunity, you may do so at the Breadwinner Professional edition and up.
To Populate the Custom Transaction Number from an Opportunity Custom Field (which requires Breadwinner Professional and up) please specify which custom field you want in the Breadwinner tab, in the Invoice Configuration section, and make sure Custom Transaction Numbers are Enabled (use the screenshots below, which explain how to disable it)
Alternatively, if you wish do Disable Custom Transaction Numbers, then in QuickBooks Online, click the gear and follow the screenshots.
Click Company Settings
Click Sales, then click the Pencil
Uncheck the Custom Transaction Number setting and Save
Custom Transaction Numbers for Purchase Orders
Custom Transaction Numbers for Purchase Orders are Enabled/Disabled separately from Invoices. To enable/disable, in QuickBooks Online please go to Company Settings, then click Expenses, and then click the pencil by Purchase Orders.
From there, please check (or uncheck) the Custom Transaction numbers setting. If checked, then you can supply Purchase Orders with your own number. This number should be a custom field on the Opportunity you are creating Purchase Orders from, and should be set in the Breadwinner Settings for Purchase Orders.