Council Rates Postponement Interest Rate in South Australia
How the Interest Rate Is Set
Under Section 182A(12) of the Local Government Act 1999, postponed council rates in SA accrue interest at a legally prescribed rate calculated as:
Prescribed annual rate = Cash Advance Debenture Rate (CADR) + 1%
The CADR is the benchmark borrowing cost published annually on 1 July by the Local Government Finance Authority of South Australia (LGFA). It fluctuates with broader interest rate conditions. The council does not set this rate — it is determined by the LGFA.
Interest is compounded monthly, not annually. The effective monthly rate is the prescribed annual rate divided by 12.
What the Numbers Look Like in Practice
Assuming a CADR of 4% (prescribed rate of 5%, monthly rate of approximately 0.417%):
Scenario: Deferring $1,000 per year for 10 years
| Year | New Rates Deferred | Cumulative Principal | Interest That Year | Total Debt |
|---|---|---|---|---|
| 1 | $1,000 | $1,000 | $27 | $1,027 |
| 3 | $1,000 | $3,000 | $135 | $3,242 |
| 5 | $1,000 | $5,000 | $255 | $5,690 |
| 7 | $1,000 | $7,000 | $386 | $8,395 |
| 10 | $1,000 | $10,000 | $610 | $12,995 |
After 10 years, interest accounts for roughly $2,995 of the $12,995 total — about 23% of the outstanding balance. On a $750,000 property, the entire debt represents under 2% of equity.
Why Monthly Compounding Matters
Annual interest of 5% compounding monthly produces a slightly higher effective rate than 5% compounding annually. The difference is small in any single year, but it accumulates over a long deferral period.
The practical impact: in years 1 through 3, interest is modest. By years 7 through 10, you are paying interest on interest on interest. The total debt curve steepens as the deferred principal grows.
This is not a reason to avoid postponement — the rates are moderate compared to commercial loans. But it is a reason to understand the trajectory before signing up for a multi-year deferral.
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How It Compares to Other Borrowing
At 5% compounding monthly, the prescribed postponement rate sits below most personal loan rates and well below credit card rates. If the alternative to postponement is falling behind on rates and incurring the statutory 2% late payment penalty plus fines, postponement is the cheaper option.
If the alternative is paying rates from savings or pension income without difficulty, postponement adds an unnecessary interest cost to the household balance sheet.
When the Interest Stops
Interest continues accruing on the outstanding balance until it is paid. Under Section 182A(4), postponed rates become due when title to the land is transferred or a postponement condition is breached. Section 182A(6) also allows you to pay all or part of the amount earlier, together with accrued interest.
Running Your Own Numbers
The SA Council Rates Help guide includes a postponement decision worksheet where you plug in your actual annual rates, property value and expected deferral period to see the interest impact specific to your situation.
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