Offset Mortgage NZ — How an Offset Account Saves You Interest

An offset mortgage links your savings account balance directly to your mortgage, reducing the interest charged on your home loan. In New Zealand, offset accounts are offered by a limited number of lenders — but for borrowers who maintain significant savings, they can deliver meaningful interest savings without sacrificing liquidity.

How an Offset Mortgage Works

With an offset mortgage, your savings account balance is “offset” against your mortgage principal before interest is calculated.

Without offset: $500,000 mortgage → interest charged on $500,000 With offset: $500,000 mortgage, $50,000 in offset savings → interest charged on $450,000

You don’t earn interest on your savings account — instead, your savings reduce the interest charged on your mortgage. Because mortgage rates are higher than savings rates, this is typically more efficient than earning savings interest separately (and savings interest is taxable; mortgage interest savings are not).

Interest Saving Example

Mortgage: $600,000 at 5.55%, 30-year term Offset savings: $40,000 maintained in offset account

Annual interest without offset: ~$33,300 Annual interest with offset: $600,000 − $40,000 = $560,000 × 5.55% = ~$31,080

Annual interest saving: ~$2,220

Comparison to savings account: $40,000 in a savings account at 4.5% = $1,800 gross interest. After 33% tax = $1,206 net.

Offset saving ($2,220) vs savings account after-tax ($1,206) = $1,014/year better off with offset.

The advantage grows as your mortgage rate rises or your savings balance increases.

Offset vs Redraw: Key Differences

Feature	Offset account	Redraw facility
How savings reduce interest	Savings balance offsets principal	Extra repayments reduce principal
Liquidity	Fully liquid — withdraw any time	May be locked during fixed rate period
Effect on mortgage term	Can shorten term or reduce repayment	Typically shortens term or reduces repayments
Availability	Limited NZ banks	More widely available
Complexity	Slightly more complex to understand	Simpler

Key difference: Offset funds remain in your savings account — fully accessible. Extra repayments into a fixed rate mortgage may not be accessible until the fixed term expires. For borrowers who may need their savings buffer (emergency fund, business capital), offset is preferable.

Which NZ Banks Offer Offset Mortgages?

Offset accounts are less common in New Zealand than in Australia. As at 2026:

Kiwibank: Offers an offset account as part of its mortgage products
BNZ: The BNZ TotalMoney account allows 100% offset across linked savings and transaction accounts
HSBC: Offers an offset product (note: HSBC has limited NZ retail presence)

ANZ and Westpac: Do not currently offer a traditional offset account in NZ. ASB does not offer offset. Check current product availability with specific banks as this changes.

The BNZ TotalMoney Account

BNZ’s TotalMoney is one of the most well-known offset products in New Zealand. It allows you to link multiple BNZ accounts (savings, cheque, term deposits) to your mortgage, with all balances offsetting against the mortgage principal.

Features:

Up to 10 accounts can be linked
Fully transactional accounts (no restriction on deposits or withdrawals)
Works on both floating and fixed rate portions
Particularly effective for business owners or people with variable cash flow

When Does an Offset Mortgage Make Sense?

Offset mortgages work best for borrowers who:

1. Maintain significant savings balances — the benefit scales with your average savings balance. If you regularly hold less than $10,000 in savings, the offset benefit may be modest.

2. Have variable cash flow — freelancers, contractors, business owners, or people with variable bonuses benefit from offsetting when cash is high (reducing interest) without locking funds in the mortgage.

3. Have an emergency fund — rather than parking an emergency fund in a savings account earning 4%, offset it against the mortgage and earn the effective mortgage rate (5.55%) risk-free.

4. Have an investment property — if offsetting against an owner-occupier mortgage while the rental property builds equity, the tax-free interest saving improves overall return.

When Offset Is Less Beneficial

Low savings balances: If you regularly hold less than $5,000 in savings, the offset benefit is minimal
High-rate fixed mortgage: Most NZ banks only offer offset on floating rate components — if most of your mortgage is fixed, offset may have limited application
Better investment returns available: If you can earn more than 5.55% after tax elsewhere (investing), directing savings to offset is not necessarily optimal

Revolving Credit vs Offset

Revolving credit mortgage (like a large overdraft facility secured against your home) is sometimes confused with an offset mortgage:

Feature	Revolving credit	Offset account
Structure	Your mortgage IS your current account	Separate accounts linked
Interest calculation	Daily on outstanding balance	Daily on mortgage minus savings
Flexibility	Complete	High
Discipline required	High (no structure)	Moderate
NZ availability	Common (ANZ, ASB, etc.)	Limited

See Revolving Credit Mortgage NZ for a full comparison.

Offset Mortgage + Fixed Rate: What You Need to Know

Most NZ banks apply offset only to the floating rate portion of a mortgage. If you have a split mortgage (part fixed, part floating), offset applies to the floating component only.

Implication: If you want offset functionality on most of your mortgage, you need a significant floating rate component. This is a trade-off — floating rates are currently ~7.09% vs fixed rates at 5.45–5.69%. The offset saving would need to exceed this rate difference to justify staying on floating.