How a $10,000 Credit Card Limit Silently Reduces Your Borrowing Power (Even with a $0 Balance)

A quick heads-up: The information in this article is designed as a general educational guide only and does not constitute personalised financial, tax, or legal advice. Because everyone's situation is unique (and bank policies change frequently), we recommend speaking with a licensed Financial Adviser to see how this applies to your specific circumstances. For full transparency on our terms of service, how we are remunerated by lenders, and any specific situations where a fee may apply, please read How We Get Paid.

You are diligent with your money. You have a credit card with a $10,000 limit, you use it to collect Airpoints on your weekly grocery shopping, and you clear the balance back to zero every single month without fail.

In your eyes, you are the model borrower.

When you submit a home loan application, however, the bank's credit assessment software looks at that exact same card through a completely different lens. To a mortgage underwriter, that well-managed card isn't proof of good financial behaviour—it is a $10,000 potential liability sitting in the background, quietly eating away at how much you can borrow for a house.

Here is why banks assess credit cards the way they do, why holding a card to build your credit score is unnecessary in New Zealand, and what you can do before you apply.

Why you don't need a credit card to build a credit score in NZ

A lot of first-time buyers hold onto credit cards simply because they have been told they need one to build a credit rating.

While taking on debt to establish a credit profile is standard advice in countries like the United States, it is largely a myth in New Zealand.

Why banks look at your limit, not your balance

When you apply for a mortgage, lenders are bound by responsible lending regulations under the Credit Contracts and Consumer Finance Act (CCCFA). Their assessment cannot just look at what you owe today; they must assess what you could legally choose to spend tomorrow.

Even if your credit card statement shows a $0 balance right now, you retain the legal right to walk out of the bank, walk into an appliance store, and max out that entire $10,000 limit the following day.

Because that facility remains open, the bank's servicing calculator must stress-test the worst-case scenario: they assume the card is fully drawn to its maximum limit, and they factor the required ongoing repayments into your monthly expenses.

How a $10,000 credit limit wipes out $50,000 of borrowing power

While every retail lender uses a proprietary servicing calculator, banks typically assess credit card commitments by assuming a monthly repayment of 3% to 5% of the total limit.

Overdrafts, store cards, and Buy Now Pay Later

This calculation does not just apply to standard Visa and Mastercard facilities. Lenders apply the exact same maximum limit methodology across nearly all short-term credit lines:

• Arranged Overdrafts: Even if your everyday account never drops below zero, an arranged $2,000 overdraft facility is assessed as a live debt.
• Store Cards: Facilities such as Q Card or Gem Visa are treated with the same strict monthly percentage calculations as standard credit cards.
• Buy Now Pay Later (BNPL): Services like Afterpay and Zip that offer revolving credit limits are reviewed closely. Frequent BNPL activity can signal reliance on short-term credit, and open accounts are factored directly into your debt commitments.

Practical steps to take before submitting your application

If you are planning to purchase a property in the next six to twelve months, reviewing your short-term credit facilities is one of the quickest ways to strengthen your borrowing position:

• Reduce Limits to Match Reality: If you only use a card for everyday expenses and clear $1,500 each month, keeping a $10,000 or $15,000 limit works against you. Lowering the limit through your mobile banking app to $2,000 immediately recovers substantial borrowing capacity.
• Close Redundant Facilities: Look through your accounts for dormant store cards, legacy overdrafts, or unused BNPL profiles and close them down permanently.
• Get an Account Closure Letter: If a bank approves your home loan subject to closing a credit card, simply cutting up the card or zeroing the balance is not enough. The bank will require a formal Account Closure Letter from the card issuer confirming the account is formally terminated before they release mortgage funds.
• Run the Numbers First: You do not necessarily have to close every card. If your income easily covers the borrowing amount you need and you value card travel insurance or reward points, keeping a modest limit may fit your plans cleanly.

Let's check your numbers before you apply

Credit limits are just one variable in a wider credit assessment. Rather than guessing how a bank underwriter will view your facilities, running your profile through bank-specific calculators before you submit an application ensures your borrowing capacity is fully optimised.

At Home Loan Factory, we assess your complete financial profile across multiple lenders, identify where credit limits might be restricting your borrowing power, and give you practical, step-by-step guidance to get your application approved.

Want to see how your credit limits are impacting your borrowing power? Get in touch with the team at Home Loan Factory today to explore your options with a clear, zero-obligation chat.