It makes sense to me. I'd make the maximum overpayment possible, wait a day for that to go through, and then ask the mortgage company how much to pay off the rest.
They could only charge ERC on an amount other than the outstanding balance if the T&Cs said they could. There could, theoretically, be a clause in there to say "ERC is due on the outstanding balance and any overpayments made within 12 months of the early repayment." but I really doubt they'd have that anywhere.
Looking at my most recent mortgage statement (Santander) I can see that the "cost to pay off the mortgage now" figure takes into account the remaining overpayment allowance rather than a blanket application of the ERC across the whole outstanding sum.
It makes sense to me. I'd make the maximum overpayment possible, wait a day for that to go through, and then ask the mortgage company how much to pay off the rest.
They could only charge ERC on an amount other than the outstanding balance if the T&Cs said they could. There could, theoretically, be a clause in there to say "ERC is due on the outstanding balance and any overpayments made within 12 months of the early repayment." but I really doubt they'd have that anywhere.
Looking at my most recent mortgage statement (Santander) I can see that the "cost to pay off the mortgage now" figure takes into account the remaining overpayment allowance rather than a blanket application of the ERC across the whole outstanding sum.
Other mortgage providers may differ.