IAS vs BAS: Instalment Activity Statements

An IAS is an instalment activity statement used to report PAYG withholding or PAYG instalments when there is no GST to report for that period. A client can receive an IAS, a BAS or both, depending on their tax registrations and reporting cycles.

What an IAS is and Which Clients Get One

An instalment activity statement is an ATO reporting document for tax obligations that do not include GST for the period. PAYG withholding is tax withheld from payments such as wages. PAYG instalments are prepayments of the client’s own income tax on business and investment income.

Clients who receive an IAS include employers that are not registered for GST and individuals or trusts that pay PAYG instalments. A GST-registered employer can also receive monthly IAS documents when its withholding cycle is monthly and its GST cycle is quarterly.

The ATO’s supported activity statement forms include IAS forms for withholding, instalments and combinations that include FBT instalments. Read the actual form type before deciding which obligations need attention.

IAS also stands for International Accounting Standards, including IAS 7 on cash flow statements. This article covers the ATO’s instalment activity statement.

IAS vs BAS: What Each One Reports

The main difference between an IAS and a business activity statement is GST reporting. A BAS can combine GST with other tax obligations, while an IAS reports obligations without GST for that period.

Feature	IAS	BAS
GST registration	Common for clients without GST registration, but also used between quarterly BAS lodgments	Used to report GST obligations for a registered client
GST	No GST labels	GST labels for the client’s reporting method
PAYG withholding	Where the form includes withholding	Where the form includes withholding
PAYG instalments	Where the form includes instalments	Where the form includes instalments
FBT instalments	Included on some IAS forms	Included on some BAS forms
Fuel tax credits, wine equalisation tax and luxury car tax	Not reported on the IAS forms in the ATO’s PLS list	Included on relevant BAS forms
Frequency	Monthly or quarterly, with an annual PAYG instalment form for eligible clients	Monthly, quarterly or annual, depending on the obligations

A medium withholder that reports GST quarterly receives an IAS for the first two months of the quarter. Its quarterly BAS combines the third month’s withholding with quarterly obligations. The client therefore receives both documents without reporting the same withholding twice.

These fictional client examples show how the rules apply.

Client	Expected documents	Reason
A café registered for GST with quarterly GST and small-withholder reporting	Quarterly BAS	GST and quarterly withholding share one statement
A landlord without GST registration, entered into PAYG instalments	IAS or PAYG instalment notice	Income tax instalments apply without GST reporting
A company with payroll	IAS, BAS or both	GST registration and the withholding cycle decide the combination

A PAYG instalment notice is different from an activity statement. When the client pays the amount shown on the notice without varying it, lodgment is generally unnecessary.

IAS Due Dates for Monthly and Quarterly Clients

A monthly IAS with only a monthly withholding obligation is normally due 21 days after month-end. Quarterly IAS obligations generally allow 28 days after quarter-end, with a longer standard deadline for quarter 2.

Use this timing table for ordinary reporting cycles, then use the due date shown on the client’s issued document.

Document or obligation	Standard timing	What changes the deadline
Monthly IAS	21 days after month-end	Weekend or public holiday adjustment
Quarterly PAYG instalments, quarters 1, 3 and 4	28 days after quarter-end	Eligible electronic or registered-agent concession
Quarterly PAYG instalments, quarter 2	The ATO’s extended quarter-2 deadline	Use the official deadline rather than the usual 28-day calculation
Quarterly PAYG instalments for a consolidated head company	21 days after quarter-end	Excluded from the ordinary registered-agent concession

The ATO’s PAYG instalment deadlines identify the exact quarterly boundaries. Its registered-agent activity statement program sets out concession eligibility.

Eligible quarterly IAS lodgments can receive registered-agent extra time. The concession requires electronic lodgment and applies to eligible statements generated after the previous statement was lodged electronically. A first statement or one following a paper lodgment can have an earlier deadline.

Monthly withholding-only statements do not receive this extra time. Quarterly PAYG instalment notices, monthly PAYG instalment obligations and consolidated head-company instalment statements are also excluded. Quarter 2 has no further ordinary agent extension.

When the due date falls on a weekend or public holiday, lodgment and payment can occur on the next business day. Keep BAS deadlines and agent concessions separate when explaining the client’s GST obligations.

Monthly IAS and the Withholding Threshold

A medium withholder withholds $25,001 to $1 million per financial year and reports and pays withholding monthly. The ATO’s small and medium withholder guidance sets these bands.

The threshold measures tax withheld, not wages paid or business turnover. A small withholder withholds $25,000 or less and normally reports quarterly. Small withholders can arrange monthly reporting.

The ATO reviews withholding cycles against annual withholding. If it changes the client’s cycle, its letter tells the client when the new reporting and payment obligations begin. Obtain that letter and update your tax software and payment reminders before the change takes effect.

Large withholders have a different electronic payment timetable linked to withholding events. Do not apply the monthly IAS routine to a large withholder’s payments.

PAYG Instalment Amount or Rate on the IAS

PAYG instalments use either an amount calculated by the ATO or an ATO-supplied rate applied to instalment income. The options available appear on the client’s document.

With the amount option, the client pays the stated instalment unless you vary it. Under the rate option, calculate the period’s instalment income and multiply it by the stated rate. Instalment income is generally gross business and investment income, excluding GST and capital gains.

For an individual or trust, automatic entry requires all the following conditions under the ATO’s entry thresholds.

• Instalment income in the latest tax return is at least $4,000.
• Tax payable on the latest notice of assessment is at least $1,000.
• Estimated, or notional, tax is at least $500.

Companies and super funds have different entry tests. A client can also enter voluntarily, so the threshold alone does not identify every instalment payer.

If the client’s expected tax falls, consider a variation using the ATO’s variation instructions.

1. Estimate tax on instalment income for the full income year using the changed income and deductions.
2. Account for instalments already paid and any variation credits when calculating the new amount.
3. Enter the variation and reason on the statement or notice before the instalment deadline and before lodging the tax return.
4. Retain the estimate and monitor later changes in income.

A lower income figure already reduces a rate-based instalment. Vary the rate when the relationship between income and expected tax changes, such as when fixed deductions remain high.

An estimate that is too low can expose the client to general interest charge. The ATO’s guidance warns that varied instalments below 85% of total tax payable can attract interest on the shortfall. A variation changes prepayments, not the final income tax liability.

Lodging and Paying an IAS for a Client

You can find outstanding IAS documents in Online services for agents and lodge them there or through compatible Standard Business Reporting software. The practitioner lodgment service, or PLS, supports the ATO’s listed IAS forms.

In Online services for agents, follow the ATO’s activity statement instructions.

1. Select the client, then open Lodgments and Activity statements.
2. In For action, select the relevant account and choose Prepare beside the issued statement.
3. Complete each applicable obligation, review the amount owing and obtain the client’s required declaration.
4. Sign the agent declaration and lodge. Save the receipt and payment details with the client’s file.

If the issued IAS has nothing to report, complete the applicable labels with zero and lodge it. A quiet period does not cancel an issued statement. An ATO-calculated instalment does not become nil merely because the client earned no income that period. Use a valid variation if the amount needs to change.

To stop future IAS documents, deal with the underlying registrations or instalment obligations. The ATO can remove a client from PAYG instalments when the relevant exit conditions apply. Cancelling withholding obligations also requires the client to have stopped making payments that require withholding. Resolve outstanding statements separately.

The client pays using the payment reference number shown in their online account or issued document. ATO payment options include BPAY and card payments. Give the client the reference for the correct account and allow time for payment processing.

Lodgment does not pay the balance. An unpaid balance remains a debt and can attract interest. If the client cannot pay in full, address an ATO payment plan separately while keeping lodgments current.

IAS Questions to Settle When a Client Comes on Board

Confirm the client’s actual activity statement obligations before promising a reporting schedule. A business description or payroll figure alone does not tell you every document the ATO issues.

Collect the following information during onboarding.

• GST registration status and reporting frequency.
• PAYG withholding registration, cycle and any cycle-change letter.
• The latest PAYG instalment entry notice, amount or rate.
• Outstanding IAS documents and payment balances left by the previous agent.
• The latest lodged statement and its receipt, so you can identify the next period and concession eligibility.

Open the ATO activity statement list and match each outstanding period to its form type and due date. Assign responsibility for preparation, client approval and payment. Use a separate BAS preparation checklist for the records needed each GST reporting period.

For a fictional sole trader without GST registration, explain that the instalment document prepays income tax and does not report GST. Establish whether the ATO issued an IAS requiring lodgment or an instalment notice requiring payment only.

For a client with quarterly GST and monthly withholding, explain that two monthly IAS documents and one quarterly BAS normally cover each quarter. Put each issued deadline and payment responsibility in the client’s welcome instructions, so the client knows what to send and what to pay.