Overdraft: How It Works, Costs, Eligibility

What is an overdraft?

An overdraft is a short-term credit facility attached to a bank transaction account that lets you spend more than your available balance up to an agreed limit. It's designed for cash-flow smoothing and unexpected shortfalls — not long-term borrowing. When you use an overdraft you pay interest and sometimes fees on the overdrawn amount. For example, if your account balance is $1 and you authorise a $1,000 overdraft, you can make payments up to that limit and interest will accrue only on the amount you actually use.

For a quick comparison with other credit types see Line of Credit and Credit Card.

How an overdraft works

An overdraft facility sets an overdraft limit and an interest rate, usually a margin above the bank's reference rate. Key distinctions:

Authorised vs unauthorised overdraft

An authorised overdraft is one where the bank agreed a limit with you in advance. Interest and any commitment fees apply, but transactions within the limit are treated as normal banking.

An unauthorised overdraft occurs when you exceed your agreed limit or have no facility. Banks often charge higher fees, may dishonour payments, and can apply default interest.

Usage mechanics

You only pay interest on the amount and days you're overdrawn. The order in which the bank processes credits and debits during the day can affect whether an item hits your overdraft. Facilities can be revolving (you can reuse as you repay) or temporary (one-off short-term limit).

Types of overdraft

Personal overdraft — linked to a transaction account for everyday spending, often unsecured with modest limits.

Business overdraft — larger limits, tailored to working-capital needs; may be secured or require financial covenants.

Secured vs unsecured

A secured overdraft uses collateral such as a property mortgage, business assets, or director guarantees. Security usually lowers the margin. An unsecured overdraft has no collateral but typically carries higher interest and stricter limits.

Revolving vs temporary

A revolving overdraft allows ongoing use and repayment. A temporary overdraft is a short, fixed-period arrangement for seasonal cash shortfalls.

Related topics: Invoice Discounting and secured loans.

Rates, fees and how interest is calculated

Typical cost components include:

• Interest rate (margin) — quoted as a p.a. rate (illustrative ranges: 8–20% p.a.; varies by lender and security).
• Establishment fee — one-off set-up charge (less common for simple personal overdrafts).
• Ongoing/commitment fee — monthly or annual fee for providing the facility.
• Dishonour/NSF fee — charged when a payment bounces or is declined.
• Default or unauthorised fees — higher charges or penalty interest when limits are breached.
• Review/arrangement fees — periodic administrative fees for review or renewal.

Interest is normally calculated daily on the outstanding overdrawn balance. Use this formula:

Interest = Balance × (Annual rate ÷ 365) × Days overdrawn

Worked example

Overdrawn amount: $1,000 Annual rate: 14% p.a. Days overdrawn: 30

Calculation: Daily rate = 0.14 ÷ 365 ≈ 0.0003836 Interest = $1,000 × 0.0003836 × 30 ≈ $17.53

So a $1,000 overdraft for 30 days at 14% p.a. costs about $17.53 in interest (plus any fees). Rates and fees vary; always check current product terms and the provider's disclosure statement. For market-rate context see the Reserve Bank of Australia: https://www.rba.gov.au/

Comparison: Overdraft vs other credit products

Overdrafts suit unpredictable, short-term shortages. Lines of credit combine flexibility with typically lower margins for larger, secured facilities. Credit cards offer convenience and rewards but can be costly if balances are carried. Short-term loans provide certainty of repayment amounts but less flexibility.

Internal cross-references: Business Loan and Overdraft.

Eligibility and documentation

Common criteria for personal overdrafts:

• Regular income (payslips, bank statements)
• Identification (ID, proof of address)
• Reasonable credit history

Common criteria for business overdrafts:

• ABN and business registration
• Recent business bank statements
• BAS statements and profit & loss / balance sheet
• Evidence of cash-flow (invoices, contracts)
• Director/owner personal financial statements and ID

Typical documents:

• 3–6 months of bank statements
• Last 2–3 years of financial statements (business)
• Recent payslips or income proof (personal)
• ASIC company extract or ABN registration (business)

See related: Business Loan and Credit Rating.

How to apply and what to ask your bank

Step-by-step:

1. Review your cash-flow needs and decide a desired limit and term.
2. Collect documents (bank statements, payslips, BAS, financials).
3. Compare providers' rates, fees and terms.
4. Apply online or at a branch — provide supporting documents.
5. Negotiate margins or fee waivers where possible.
6. Confirm the facility in writing and note review/expiry dates.

Key questions to ask:

• What is the interest rate and how is it calculated?
• Are there establishment, commitment or review fees?
• What happens if I exceed the limit (unauthorised fees)?
• Is the overdraft repayable on demand or reviewed periodically?
• Will you require security or personal guarantees?
• Can I get a temporary increase for seasonal needs?

When to use — pros and cons

Pros:

• Immediate access to cash when balances fluctuate.
• Interest only on amounts used; flexible repayment.
• Convenient for managing timing gaps (e.g., supplier payments vs receivables).

Cons:

• Can be expensive if used long-term (interest + fees).
• Risk of banks reducing or cancelling the facility, which can disrupt cash flow.
• Unauthorised overdrafts attract high fees and can harm supplier relationships.
• Rolling overdraft debt can mask the need for longer-term finance (e.g., a term loan).

Better alternatives when:

• You need predictable, longer-term funding — consider a Business Loan or a secured loan option.
• Purchases require interest-free periods and rewards — compare Credit Card.
• You want a structured revolving facility with lower margins — review Line of Credit.

Practical tips to manage and minimise costs

• Monitor balances daily and set low-balance alerts with your bank.
• Confirm whether interest is charged daily or monthly and how transaction ordering works.
• Negotiate a lower margin or waiver on commitment fees, especially on renewal.
• Avoid unauthorised overdrafts — arrange a temporary increase if needed.
• Reassess annually: if usage is persistent, switch to a longer-term loan to reduce interest.
• Keep documentation handy to speed up limit reviews or increases.
• Reconcile transaction ordering (credits often processed before debits) to reduce accidental overdrafts.

For wider cash-management tactics, see Invoice Discounting.

FAQ

Key takeaways

An overdraft is a flexible short-term credit facility ideal for managing cash-flow gaps, but it's expensive for long-term borrowing and carries the risk of unexpected fee escalation. Understand the difference between authorised and unauthorised overdrafts, compare rates and fees across providers, and consider switching to a term loan or line of credit if you use the overdraft regularly. Always ask your bank about current rates, fees, review periods, and security requirements before committing.

This article is general information only and is not legal, tax or financial advice.