Mortgage cashback can look like free money. In 2026, it is one of the biggest reasons homeowners are asking whether they should refinance.
But the real question is not whether the cashback is large. The question is whether the total refinance deal leaves you better off after every cost, every condition, and every structural trade-off.
This article is the calculation companion to our main NZ refinancing plan.
Why Cashback Matters In 2026
The RBNZ May 2026 Financial Stability Report gives unusually clear context. RBNZ says "Mortgage refinancing between banks was elevated" late last year when mortgage rates were near their lowest point and more fixed loans were rolling over.
During that period, RBNZ says banks offered new customers up to 1.5 percent of their mortgage balance as an upfront payment, compared with typical levels of around 0.9 percent. It also says "nearly three times the usual amount" of mortgage debt switched banks in December.
That does not mean every borrower should chase cashback. It means cashback is now a meaningful part of the refinance equation, especially for larger mortgages.
The Costs To Count
A refinance can include legal costs, bank discharge fees, new loan documentation costs, valuation costs, break costs if you leave a fixed term early, and possible clawback of cashback from your existing bank.
Some costs are small. Some are not. Break costs can be the big one, especially if your fixed rate is higher than current wholesale rates or if there is still a long time left on your term. Read how to calculate break costs before assuming the refinance savings will be easy.
You should also check whether the new lender's cashback has a clawback period. If you refinance again, sell, or repay the loan too soon, you may have to repay some or all of the cashback.
The Break-Even Test
Start with the expected savings from the new mortgage. Compare your current repayments and rate structure with the proposed new structure over the period you are actually comparing.
Then add the new lender cashback. Subtract legal costs, valuation costs, discharge costs, break costs, and any existing cashback clawback.
If the remaining benefit is strong, refinancing may be worth it. If the benefit is thin, you may be better to refix, wait until your fixed term ends, or negotiate harder with your current lender.
Rate Is Not The Whole Deal
A low rate can still be the wrong answer if the loan structure is poor. For example, you might need an offset account, a revolving credit facility, split fixed terms, or a separate loan split for renovation or business borrowing.
The RBNZ OCR decision in May 2026 notes that higher wholesale interest rates were passing through to higher fixed-term mortgage rates. That means the timing of your fixed terms matters. A single short-term rate may look attractive, but it may also leave your whole mortgage exposed at the same time.
This is why your refinance calculation should include structure, not just dollars.
Watch The Clawback
Cashback usually comes with conditions. A common condition is that you must keep the lending with the bank for a set period. If you leave early, you may need to repay some or all of the incentive.
That matters if you plan to sell, restructure, renovate, separate property ownership, or move lending again soon. A large cashback is less useful if it traps you in a structure that does not suit the next stage of your life.
It also matters if you already received cashback from your current lender. A refinance can sometimes create two clawback questions at once: whether you must repay your old incentive, and whether the new incentive locks you into the new bank. Both should be visible in the calculation before you sign.
When Cashback Can Be Worth It
Cashback can be genuinely useful when it offsets real switching costs, the new lender provides a better loan structure, the rate is competitive, and you are likely to keep the mortgage long enough to avoid clawback.
It can be less useful when you are switching only for the upfront payment, when the rate is not competitive, or when the refinance adds complexity without improving your mortgage plan.
The Mortgage Lab Approach
Mortgage Lab would normally compare your current bank's retention offer against the refinance offer. That means rate, cashback, break cost, legal cost, clawback, repayment structure, loan term, and future plans all get tested together.
The best refinance is not the one with the flashiest incentive. It is the one that leaves you in the best position after the full calculation.
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