Lender small print, sourced and dated
Santander: the mortgage dates and limits that cost money
These are the Santander rules that decide when overpaying is free, when leaving is cheaper, and how early your next deal can be locked. Every figure links to the lender's own published page with the date we last checked it — and where their public pages don't confirm a detail, we say so instead of guessing.
| Penalty-free overpayment allowance | 10% of the fixed-rate loan, each calendar year (January to December) · Santander's published policy, checked 2026-08-15 |
|---|---|
| Early-lock (product transfer) window | ~4 months before your deal ends · industry guide, checked 2026-08-15 |
| Overpaying beyond the allowance | The excess is normally charged at your deal's early repayment charge rate — the percentages and step-down dates are in your mortgage offer. |
Turn the rules into your dates
Rules only save money on the days they apply to your own deal: the day the allowance resets, the day the charge steps down, the day the lock window opens. Work out your remaining Santander allowance free, or build your full timeline in two minutes. A watch then emails you before each date — £7.99, once, no commission from Santander or anyone else.
Frequently asked questions
How much can I overpay on a Santander mortgage without a charge?
Santander's published rule is 10% of the fixed-rate loan, each calendar year (January to December). Overpayments beyond that are usually charged at your deal's early repayment charge rate. Your own offer document is the definitive statement.
When does the Santander overpayment allowance reset?
It resets each calendar year (January to December). Unused allowance does not carry over.
How early can I lock a new deal with Santander?
Santander's product-transfer window opens about 4 months before your current deal ends — you can select a new deal that starts when the old one finishes, and remortgaging elsewhere typically allows up to 6 months.
WatchMyMortgage is independent and takes no commission from Santander or any lender. Rules summarised from the linked public pages on the dates shown; lenders change terms, and your mortgage offer is the definitive statement of yours. This is information, not financial advice; for advice on your circumstances, speak to a mortgage adviser regulated by the FCA.