"Does quicken calculate a payment made late with additional interest".
I probably should have phrased the first sentence in my first post slightly differently:
"Quicken doesn't have any "adjust for missed [or late] payment" loan feature ...".
That really says it all as far as what Quicken will do if you do not follow the Quicken loan payment schedule.
If you need to change the loan payment schedule or any specific loan payment, you need to do it manually.
And if you've missed a payment, I suspect the job will call for changing the loan payment schedule (the loan itself). In your example, if the only change you make after a missed payment is to add the missed interest to the next payment ... I don't see how the existing payment schedule can still be used. The payment schedule assumed every payment would be made on time and the loan balance would be reduced by the scheduled principal amount with each payment. In your example, you're leaving out (postponing, if you will) one principal payment.
Enter new the balance the date you want the amortization to show this change.
After you do this, you will see an entry in your loan's ledger for a "Balance Adjustment". I would categorize this entry under whatever category you're using for the loan's interest. Maybe put "late payment" in memo, to remind you a year from now what happened. :)
If you want to double check that the loan payments have been "recalculated" to reflect the new, higher principal amount, do this:
TOP RIGHT side in loan's register : (same as before)
-- Account Actions -- Loan Details
Click center tab for "PAYMENT SCHEDULE". Look for the adjustment entry (it's in date order) You'll see the payment breakdown of principal and interest gets modified immediately after the adjustment.