Yes, if TurboTax is asking for the ending balance, it wants the balance as of the end of the year (December 31, 2018). It is needed to determine what portion of your mortgage interest is deductible. You can find your year ending balance on a mortgage statement or by contacting your mortgage company. The beginning of the year balance should be found on your 1098 form.
You are receiving
the request in TurboTax for your ending mortgage principal balance due to the change in tax
law related to the mortgage interest deduction. There are now different
mortgage interest deduction limits based upon when the mortgage was originated
and what it was used for, so portions of a mortgage listed may include interest
that is not deductible. Therefore, the ending mortgage balance is needed
to determine the deductible portion of the interest being entered.
Here is more
information about the tax law and the provisions for now being able to deduct
mortgage interest:
https://ttlc.intuit.com/replies/3300473
