My mortgage is on fixed rate I want just to pay extra £10,000 to reduce my outstanding balance but I just pay off my 10% If any body know how much I will need pay ERC?

Hi I've got a question about my mortgage. Last week I have paid off £12.000 for my mortgage but I still have £128,068.58 left to pay. Next month I want to pay £10.000 extra do I will need to pay ERC? (early repayment charge). If yes could you explain me how it's work and how much of that £10.000 will go to pay off my outstanding mortgage balance (£128,068.58) THANK YOU