Yeah, I see people describe it like that all the time, it's never corrected, and doesn't match how I always thought mortgages in general work (and definitely doesn't match mine), so I'm never entirely sure if it's a different system from another country or just a version of the blind leading the blind. Which is why I made my comment so specific to myself.

The parent of that comment mentioning "a fee to overpay" is one I've never even heard of before. Definitely not the case here, free to pay down the principal as much as I want whenever I want as long as the current interest for the month is paid first.