Should you overpay your mortgage or save?

The perennial financial dilemma of whether to funnel surplus cash into reducing a mortgage or building up savings has been addressed by financial expert Martin Lewis, who argues the decision must be purely mathematical, particularly given the current elevated interest rate environment.

Lewis suggests that consumers must treat overpaying their mortgage as a guaranteed, tax-free rate of return equivalent to their current mortgage interest rate. Therefore, the choice between overpaying or saving should hinge on a direct comparison: if the mortgage interest rate is higher than the best available savings rate, overpaying is the more financially advantageous choice.

Crucially, savers must consider the effect of tax on their deposits. For basic-rate taxpayers, a savings account must yield a return significantly higher than the mortgage rate to compete effectively, as the interest earned on savings is taxable, while the interest saved on a mortgage is not. For example, a 5% mortgage rate effectively requires a taxable savings account to yield closer to 6.25% (or higher, depending on the tax bracket) to offer a better overall return.

However, this advice comes with crucial prerequisites. Lewis stresses that before allocating any funds to mortgage reduction, consumers must first secure an emergency fund. This fund, typically three to six months’ worth of expenditure, must be held in an easy-access account. Additionally, any existing high-interest debts, such as credit cards or personal loans, should be cleared entirely, as their interest rates almost universally dwarf those found on mortgages.

In the present climate of high fixed-term mortgage rates, Lewis notes that overpaying is often highly effective. Nevertheless, a key consideration remains flexibility. While overpaying guarantees a return, the money is locked into the property. Conversely, funds held in a savings account, while potentially offering a lower rate of return post-tax, remain liquid and accessible for immediate needs or unexpected expenses.

Ultimately, according to Lewis’s analysis, individuals must calculate their specific post-tax savings returns against their individual mortgage rate before committing to a strategy, balancing maximum potential savings with necessary financial flexibility.