Shortfall Interest Charge on Amended Assessments

Shortfall interest charge is daily compounded interest on extra tax arising from an amended assessment. Check the original payment deadline, the amendment notice and each quarterly rate before considering remission. An early payment can support relief without changing the statutory calculation period.

What the Shortfall Interest Charge Covers

For an income tax amendment, shortfall interest charge (SIC) compensates for the time the additional tax remained with your client. The additional assessed tax is the principal. A shortfall penalty concerns the conduct that produced the error. SIC can apply even when no penalty applies.

Keep each amount separate when explaining the amended assessment to your client. A penalty reduction does not automatically reduce interest, and paying the principal does not resolve an outstanding interest charge.

SIC generally covers the original tax payment deadline through the day before the Commissioner gives notice of the amendment. General interest charge (GIC) can then apply to amounts unpaid after the amended liability becomes due. Check the notices for the payment deadlines for both additional tax and SIC. SIC is ordinarily payable 21 days after notice of the charge.

This distinction also matters when reviewing a business activity statement. A goods and services tax shortfall generally attracts GIC, so an income tax SIC calculation is not interchangeable with that charge.

Check the Assessment Period and Rates

Start with the additional tax assessed, rather than the amended assessment’s total balance. The balance can include other debts or credits that do not form part of the SIC principal.

1. Match the original assessment and amendment to the same entity and income year. Retain the calculation showing the additional tax.
2. Establish the original payment deadline, including when tax would have been payable if the first assessment had shown an amount due.
3. Identify when the Commissioner gave notice of the amendment. Include the preceding day as the last SIC day.
4. Split the period at every quarterly rate change. Use the ATO’s SIC rate schedule for the days in each segment.

A later amendment that reinstates an item reduced by an earlier amendment can have a different start point. Trace that item through the assessment history instead of applying the first assessment’s deadline to every adjustment.

The SIC rate uses a base interest rate plus three percentage points. Divide the annual rate by the number of days in that calendar year to obtain the daily rate. Daily compounding adds earlier SIC to the amount on which the next day’s interest is calculated.

An advance payment does not itself stop statutory SIC. Record the payment for a separate remission calculation. A processing delay also needs a remission assessment, rather than an invented end date in the original calculation.

Reconcile an Illustrative Charge

Assume a fictional company has a $20,000 income tax shortfall over 35 chargeable days. Its amendment notice ends the period after 20 days at one quarterly rate and 15 days at the next. There are no payments, offsets or remissions in this example.

The illustration uses two consecutive rates from the ATO schedule: 7.43% and 7.51% a year. Both segments fall within a 365-day calendar year. These are period-specific assumptions, not a rate to apply to another assessment.

Daily Compounding Across the Rate Change

Segment	Days	Annual rate	Calculation of closing amount	SIC added
First rate period	20	7.43%	$20,000 multiplied by (1 + 0.0743 / 365) to the power of 20	$81.58
Second rate period	15	7.51%	Unrounded first closing amount multiplied by (1 + 0.0751 / 365) to the power of 15	$62.07
Total	35	Two rates	Final amount less $20,000 principal	$143.65

The first closing amount is approximately $20,081.58. Carry full precision into the second segment, then round the final charge to cents. The resulting combined amount is approximately $20,143.65.

If your reconciliation differs from the notice, compare the principal first, then the included days and rate boundaries. Next inspect daily-rate precision, rounding and any separate remission credits. Ask the ATO for its calculation breakdown when those checks do not explain the difference.

A general penalty-interest estimate can help check arithmetic. It does not establish the SIC principal, the statutory period or your client’s remission entitlement. Keep the notice and account transactions beside the working paper.

Request Remission With Supporting Evidence

The Commissioner can remit SIC where it is fair and reasonable. Explain why the circumstances justify the Commonwealth bearing some or all of the delayed-payment cost. Earning less on the retained money than the SIC charged is not, by itself, a remission ground.

The ATO’s SIC remission practice statement distinguishes several situations. Unreasonable ATO delay, an audit exceeding its expected timeframe and delays outside the taxpayer’s control require different evidence. Relief can be full remission or a reduction to the base rate for the relevant period.

For a voluntary amendment, establish when the ATO received all necessary information and whether processing exceeded its published service standard. The processing-delay concession does not apply to a disclosure made after notification that a review or audit has started or will start.

For an advance payment, retain proof of receipt and allocation to the shortfall. Calculate the relevant post-payment SIC separately. The ATO’s remission policy takes account of interest on early payment, and a partial payment supports proportionate consideration.

Use a written request that another officer can follow without reconstructing the file.

1. Identify the assessment, shortfall amount and SIC charged. State the amount or period you ask the ATO to remit.
2. Set out the chronology. Attach amendment receipts, information requests and responses, payment evidence and relevant audit correspondence.
3. Connect each ground to its affected days. Explain who caused any delay and what your client did to reduce it.
4. Retain the request and lodgement receipt. Check that the acknowledgement covers SIC remission, then follow up using its reference if no decision arrives within the advised timeframe.

An unprompted tax voluntary disclosure is not an automatic right to interest relief. Its timing and surrounding circumstances can support the separate remission request. A penalty decision remains a separate decision too.

Handle Deductibility and the Outcome

The tax treatment depends on when SIC is incurred, not simply the days used to calculate it. SIC on an income tax shortfall is incurred in the year the amended assessment notice is served.

Under the deduction changes, affected SIC is non-deductible even where the underlying debt concerns an earlier income year. Earlier deductible interest retains its separate treatment. Apply the ATO’s interest deduction transition rules to the notice and your client’s income year. An approved substituted accounting period has its own commencement rule, so do not assume the standard-year transition applies unchanged.

Later remission of non-deductible SIC does not become assessable income under these rules. A remission of earlier deductible interest can be assessable. Match the credit to its original charge and deduction treatment before completing the tax reconciliation.

Use the ATO’s interest reporting guidance when reconciling account transactions. The ATO warns agents against using the Year to date interest summary report to complete returns because of recurring data issues.

After relief is granted, match the written decision to the remission credit and remaining balance. Confirm the amount and covered period, and investigate an unposted or incorrectly allocated credit before closing the request.

If relief is refused, obtain written reasons and check the available review route. For income tax SIC, a formal ATO objection to the remission decision is available where unremitted SIC exceeds 20% of the additional tax. Equality with that threshold is insufficient. Check the decision’s review instructions and deadline before acting. Where formal objection rights do not apply, consider an informal review request or legal advice on judicial review.