When I paid off my mortgage, interest rates were at 6% and my tax rate was 40%, so I would have needed a 10% pre-tax return on an investment to beat paying off the mortgage.
Would you be able to explain the math behind this please?
Sam
This is where I find out my maths was wrong! Bear in mind that mortgages work differently in the UK compared to US - nearly all of our mortgages have variable interest rates which historically could go up and down significantly, sometimes month by month. You can now fix your interest rate, but typically only for terms of 1-5 years. There is a recent trend for people to have a series of such fixes, but this was not the case in the past. There is no tax benefit to having a mortgage in the UK (unless it's on a buy-to-let property and even that is changing.)
To make it simple, let's say I had a sum of £100 000 to invest and a mortgage of £100 000 on which the interest rate back then was 6%. So interest payments of £6 000 per year. If I invested that £100k in a savings account paying interest at 10% gross, I would receive £10 000 p.a gross interest. My marginal income tax rate at that time was 40%, therefore I would pay £4 000 tax on that interest and earn £6 000 per year. So in that case, the bank account and paying off the mortgage would be equal, both earn me £6k. If I was getting a lower than 10% return therefore, paying off the mortgage made more sense (and remember that paying off the mortgage is a guaranteed, risk-free return, unlike stocks.) At the time, I could get around 4-5% interest on a bank account, so as I say, it was a no-brainer. A more sophisticated calculation would've been to recognise that the 6% was only for the remaining term of the mortgage, not in perpetuity, but given the level of inflation at the time, it doesn't change things much. Key point is that I was paying mortgage interest out of post-tax earnings, but when looking at investment rates of return, I was limited to things which I would pay tax on.
In hindsight, given the property boom in the UK, it may have been better to have mortgaged up to the hilt and bought the biggest property I could afford, or a BTL portfolio, but of course investing is easy with hindsight. (Equally, I could have bought an index tracker and the FTSE-100 is lower today than it was in 1999, so that might've been a bad move, although presumably dividends could've put me ahead.)
Ukwhat?'s situation may be different because his/her mortgage interest rate is almost certainly much lower, marginal tax rate may be different and he/she may be able to use tax-shelters like ISAs for investments. Sounds like Ukwhat? has been significantly over-paying mortgage already (going from £170k to £125k in 3 years - a normal 25 year team would see it reduce by more like £20k in that timeframe.)