UK Remortgage & Payment Shock Calculator (2026)

Mortgage payment shock refers to the sharp increase in monthly mortgage payments experienced by homeowners rolling off ultra-low fixed rates (often 1.5% to 2.2% from 2020–2021) onto prevailing market rates of 4.5% to 5.5%, frequently adding £250 to £500+ to monthly household expenses.

Most UK lenders allow you to secure and lock in a new remortgage rate up to 6 months before your existing deal expires. This protects you against further rate rises while letting you switch to a cheaper product if interest rates fall before completion.

Paying an upfront product fee (commonly £999) only makes financial sense if your loan balance is large enough for the monthly interest savings to exceed the fee cost over your fixed term (usually 2 or 5 years). For loans over £200,000, fee-paying deals usually deliver lower overall costs; for smaller balances under £120,000, fee-free deals are often cheaper.

If your fixed or tracker deal expires and you do nothing, your mortgage automatically reverts to your lender Standard Variable Rate (SVR). SVR rates are typically 7.5% to 8.5%—far higher than competitive fixed remortgage rates.

An Early Repayment Charge (ERC) is a financial penalty charged by your lender if you exit or pay off your mortgage before your fixed or discounted period ends. ERCs typically scale down by 1% per year (e.g. 5% in year 1 down to 1% in year 5).