When you migrate a company file from QuickBooks Desktop to QuickBooks Online, does all customer and vendor data automatically migrate too?

Do you need to convert data from QBD CA to QBO CA?

https://quickbooks.grsm.io/Canada

The process only focuses on converting core transactions. You need to migrate data manually for certain data types a. e.g non-posting transactions (estimate, purchase order), jobs, attachments. Another option, you may consider to purchase a 3rd party service to convert data with those additional requirements or if your Total Targets > 750K.