What is outstanding mortgage principal or origination date?

[KittyM]

Outstanding Mortgage Principal is the paid-down balance of your loan on the first day of the tax year.  It is found in Box 2 of your Form 1098 Mortgage Interest Statement.  It shows how much remains to be paid on the amount you borrowed.

The Mortgage Origination Date is the day you took out the loan.  It is found in Box 3 of your Form 1098 Mortgage Interest Statement.