All the fields needed to create a transaction may not be available in the accounting system.

Profile-based importing is excellent for off-the-shelf accounting packages such as QuickBooks Online, Peachtree, and any other system which does not have the ability to store account and routing information.
 
First, you would create profiles for each of your Customers, Employees and/or Vendors (yes, you can import profiles).
 
Then, simply export from your accounting package transactional information.  It can be as simple as an amount field and either a Name or ID number of the related profile.