In QuickBooks Online, edit the customer notes field to enter the customer's credit limit.  On a separate line in the notes field, enter "CreditLimit:" followed by the credit limit, followed by a period.   For example: 

That's it!  Within 15 minutes of you updating QuickBooks with the credit limit, the credit limit will show up in Crik-IT for rep and in-house users.

Note that this field is for informational purposes only.  Users will be able to enter and submit orders even if the customer's credit limit has been exceeded.  This is because most companies want to get the order and will manage collections and order holds on the back end.