How daily interest works on Australian home loans

Daily calculation makes timing visible

A simplified daily calculation applies the annual rate to the balance for the relevant number of days. A repayment first covers accrued interest under the lender’s process, with the remaining principal reduction lowering later daily balances. An offset can reduce the balance charged interest without reducing contract principal.

The statement may add accrued interest monthly even though it was calculated day by day. Do not confuse the frequency of charging interest with the frequency of calculating it, and do not assume every lender uses an identical implementation.

Example: two dates, one principal amount

A homeowner considers a $5,000 extra repayment either now or after a known bonus date. If the same amount is accepted without a fee, the earlier principal reduction usually affects more daily balances. Keeping the money in a fully effective offset until payment may produce a similar interest-bearing balance while preserving access, subject to account terms and fees.

The homeowner records the exact posting date and compares the next statement. The difference should not be exaggerated: future rates, withdrawals from offset and lender rounding can outweigh a small timing gap.

Inputs for a daily schedule

1. Use the current principal balance and contract rate.
2. Enter the next actual repayment date.
3. Choose monthly, fortnightly or weekly frequency correctly.
4. Separate offset money from direct principal repayments.
5. Apply extra repayments only on expected credited dates.
6. Reconcile projected interest and balance with statements.

Contract and model checks

A fixed loan can restrict extra repayments or charge a break cost. A variable loan may change rate. An offset may attract account or package fees and might not offset every loan split. These product terms matter more than a generic daily formula.

• Ask when transfers are effective for interest.
• Check whether leap years use 366 days.
• Confirm which split an offset is linked to.
• Do not enter redraw availability as offset cash.
• Rerun after any rate or repayment change.

Use a calculator as a scenario, not a promise

The Australian calculator accrues interest across actual calendar days using a 365- or 366-day year. It is transparent about that convention, but your lender’s statement remains the source for binding interest and posting amounts.

The Australian model accrues interest across the actual calendar days between repayments, using 365 days or 366 in a leap year. It supports monthly, fortnightly and weekly schedules and keeps offset separate from contract principal.

The estimate holds the entered rate constant, assumes extras reach principal and does not model redraw as offset. Lender posting, fixed limits, break costs, fees and split-loan details can produce a different result.

Review the plan before money leaves

Compare zero extra, the intended plan and a version that pauses after a household shock. Use the same starting balance, dates and rate in each run. For a variable or split loan, repeat the comparison at other rates without describing any case as a forecast.

Keep the loan contract, current statement and written lender answers about fixed limits, break costs, offset links and redraw. Model materially different splits separately, because one blended schedule can hide different expiry dates and features.

• Fund required repayments and essential bills before voluntary extras.
• Keep an accessible reserve for income shocks and home repairs.
• Verify which split receives the extra repayment.
• Check the statement after the first transaction or frequency change.
• Rerun after a rate, repayment, offset, fee or product change.