When to Fix Your Mortgage NZ — Timing Your Rate Decision

The question every NZ mortgage holder faces at rollover: fix now, or wait? And if fixing, which term? These decisions can save or cost thousands of dollars — but they involve genuine uncertainty about where interest rates are heading.

This guide gives you a clear framework for thinking through the decision.

The Fundamental Challenge: No One Knows for Certain

Rate decisions are ultimately forecasts. The RBNZ, the major banks, and financial markets all publish rate forecasts, but history shows they’re often wrong. During 2020–2022, “experts” consistently predicted rates would stay low; by May 2023, the OCR had reached 5.50%.

The goal is not to perfectly predict rates, but to make a decision that aligns with your risk tolerance, financial situation, and the balance of probabilities based on available information.

Step 1: Understand the Current Rate Environment

Before deciding when or how long to fix, understand where rates are and where they might be heading.

Key indicators to check:

Indicator	Where to find it	What it tells you
Current OCR	RBNZ website	Current short-term borrowing cost for banks
RBNZ OCR forward guidance	Monetary Policy Statement (4 times a year)	RBNZ’s own rate forecast
Wholesale swap rates	Financial markets / bank treasury pages	Market’s expectation of future rates (priced into fixed mortgage rates)
Current bank carded rates	Each bank’s website	Actual fixed rates available today
Economist forecasts	Interest.co.nz, NZ Herald, major bank economists	Independent rate predictions

The OCR so far: The RBNZ cut the OCR from 5.50% in mid-2024 to 2.25% by November 2025, then raised it to 2.50% on 8 July 2026 and 2.75% on 2 September 2026. Swap rates, which price fixed mortgage rates, reflect what markets expect the OCR to do next, so check the current picture before choosing a term.

Step 2: Choose a Term Based on Your View

If you believe rates will fall

Strategy: Fix for a shorter term (6 months or 1 year) so you can refix at lower rates when your term expires.

Example: a 1-year fixed at 5.55%
If rates fall to 4.80% in a year, you roll over at 4.80%
Total benefit: 0.75% rate reduction from the next term (illustrative rates)

Risk: If rates rise instead of fall, you’re in a worse position at rollover.

If you believe rates will rise

Strategy: Fix for a longer term (2–5 years) to lock in current rates before they increase.

Example: a 5-year fixed at 5.89%
If rates rise to 7.00% over the next 2 years, you’re protected at 5.89% for 5 years
Total benefit: significant, if rates rise significantly

Risk: If rates fall, you’re locked into a higher rate and face large break fees if you want to exit.

If you’re uncertain (the most common situation)

Strategy: Split your mortgage across multiple terms to diversify risk.

Example: 50% fixed 1 year (5.55%)
Example: 50% fixed 2 years (5.45%)

Part of your mortgage benefits if rates fall (the 1-year portion rolls over sooner). Part is protected if rates stay flat or rise (the 2-year portion locks in the rate).

This is not trying to beat the market — it’s managing uncertainty prudently.

Step 3: Compare the Rate Curve

The term structure of rates (yield curve) tells you how much extra you pay for longer certainty. Compare each bank’s carded rates for 6 months through 5 years on its own rates page: sometimes shorter terms cost more than longer ones, and sometimes the reverse. When short-term rates are higher than long-term rates, it can mean the market expects rates to fall.

The “Wrong” Decision Risk

What if I fix long and rates fall? If you fix 5 years at 5.89% (an example rate) and rates fall to 4.50% in 2 years, you have three options:

Continue paying 5.89% for the remaining 3 years (cost: ~$41,000 extra on $600,000 vs 4.50%)
Pay a break fee to exit early and refix at 4.50% (break fee could be $20,000–$40,000)
Sell the property (which also triggers the break fee)

What if I fix short and rates rise? If you fix 1 year at 5.55% and rates rise to 7.00% in 12 months, you refix at 7.00%. The cost is the rate increase applied to your balance for future terms — no break fee, just higher ongoing repayments.

The asymmetry: fixing long and being wrong creates break fee risk. Fixing short and being wrong creates repayment risk. For most borrowers, repayment risk is more manageable than large one-time break fees.

Practical Decision Framework

Fix for 1 year if:

You believe rates will fall
You want flexibility to access lower rates at rollover
You don’t need long-term payment certainty
Your budget can handle moderate repayment variation

Fix for 2 years if:

You want a balance of rate certainty and flexibility
The 2-year rate is meaningfully lower than the 1-year rate
You’re unlikely to make major financial changes in the next 2 years

Fix for 3–5 years if:

You have high income uncertainty and need budgetary certainty
You believe rates will rise significantly and want to lock in current rates
You’re taking out a large loan and any rate rise would cause genuine financial stress