How overpayments cut your term and total interest.
Interest saved
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New payoff time
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Time saved
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Your breakdown
Updates live as you type| Measure | Standard | With €200/month |
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Why an extra €200 a month moves the needle
An overpayment is any money you pay on top of your scheduled monthly mortgage repayment, and every cent of it goes straight to reducing the capital you owe. That matters because mortgage interest is charged on the outstanding balance. Knock the balance down faster and you starve the loan of the interest it would otherwise have generated for the rest of the term. This tool simulates exactly that, month by month, applying any lump sum immediately and adding your regular overpayment to each payment, then comparing the total interest you end up paying against the interest on the standard schedule.
The compounding logic behind the saving
The reason overpayments feel almost too good is compounding working in reverse. On a normal mortgage, most of your early repayments are interest and only a sliver is capital. An overpayment skips that queue and lands entirely on the capital, so it removes interest not just this month but in every month that follows. The earlier in the term you do it, the more future interest you cancel, which is why a lump sum in year one is worth far more than the same amount in year twenty. The flip side is that the saving is largest precisely when your balance, and therefore your interest, is at its highest.
€300,000 over 25 years with a €200 top-up
Take a €300,000 balance at 4 percent with 25 years left to run. The scheduled repayment is about €1,584 a month. Add €200 a month on top and the loan behaves very differently.
That €200 a month, about €50,000 of overpayments spread across the shortened term, saves over €34,000 in interest and clears the mortgage four years and four months early. The chart contrasts the two interest totals.
Check the break fee before you commit
One genuine word of caution. If you are on a fixed rate, your lender may charge a break funding fee for overpaying beyond an allowed limit, because you are repaying money they priced on a fixed term. Many Irish lenders permit a modest overpayment on a fixed rate each year without penalty, often up to 10 percent of the balance, but the exact terms vary by bank and product. Variable and tracker mortgages can almost always be overpaid freely. Before sending a large lump sum, ring your lender, confirm there is no break fee, and ask whether the overpayment shortens the term or reduces the monthly payment, because the term reduction is what produces the interest saving shown here.
Should I overpay the mortgage or invest the money instead?
It comes down to your mortgage rate versus the return you could reliably earn elsewhere, after tax. Overpaying a 4 percent mortgage is a guaranteed, risk-free 4 percent return, and the interest saved is not taxed. Beating that consistently in a deposit account or a fund, after DIRT or exit tax, is harder than it looks. Clearing expensive short-term debt first, then building an emergency fund, usually comes before overpaying.
Does a lump sum or a monthly overpayment work better?
A single lump sum early in the term saves the most per euro, because it removes interest over the longest remaining period. A steady monthly overpayment is gentler on cash flow and still produces large savings, as the example shows. Many people do both: a lump sum from a bonus, plus a modest monthly top-up.