Claude Opus 4.6 vs Claude Opus 4.8for everyday maths

**It's all about time.**

Every £100 you overpay early on stops interest being charged on that £100 for the remaining 20-plus years. Since mortgage interest compounds — meaning you're charged interest on interest — removing even a small amount early creates a snowball effect of savings that grows over decades.

Overpaying near the end only eliminates interest for the short time left, so there's far less compounding to avoid. In short, early overpayments have more *time* to work in your favour, and time is the most powerful factor.

Early in the mortgage, you owe the most money, so interest piles up fast on that large balance. Overpaying now shrinks that balance immediately, meaning every future month's interest is calculated on a smaller amount. That saving compounds year after year for the rest of the term.

In the final years, you owe very little, so there's barely any interest left to save, and hardly any time for the benefit to build up. Timing matters because interest feeds on both size and duration.