PAYG vs Estimated Tax: Why They Don't Match

General information only. This is not tax or financial advice. Consult a registered tax agent for advice specific to your situation.

Australia collects income tax in two main ways as you earn: PAYG withholding for employees, and PAYG instalments for the self-employed and investors. Both are estimates — and neither guarantees your account will be square when you lodge. Understanding how each system works, and where the gaps come from, is the starting point for avoiding a surprise tax bill.

PAYG withholding: how employers collect tax

When you are employed, your employer deducts income tax from each pay using ATO tax withholding tables. These tables take your gross pay for the period and translate it into a withholding amount, annualising the figure to approximate your full-year tax.

The withholding tables make several simplifying assumptions:

• You have one job only. The tables treat each employer’s payments in isolation, with no visibility of other income.
• You have no HELP debt. Unless you have submitted a TFN declaration or withholding variation telling your employer to withhold for HELP, no HELP repayment component is included.
• You are eligible for the tax-free threshold (if you have ticked that box) and the low income tax offset (LITO).
• Your income is steady and consistent across the year. Bonuses, commissions, or irregular payments can cause the annualised estimate to be off.

The tax withheld is sent to the ATO on your behalf, usually monthly or quarterly. At the end of the financial year, the total withheld appears on your income statement in myGov and is credited against your actual tax liability when you lodge.

PAYG instalments: how self-employed and investors pay

If you have income that is not subject to withholding — business income, rental income, dividends, interest — the ATO may require you to pay tax in advance via PAYG instalments. This usually begins after your first tax return shows business or investment income above a certain threshold.

The ATO sends you a quarterly instalment notice (or includes it in your Business Activity Statement) with a calculated instalment amount based on your prior year’s tax liability. You can either pay the ATO’s suggested amount or vary it downward if your current-year income is lower. Varying incorrectly and paying too little can result in a shortfall penalty at the end of the year.

Like withholding, instalments are a credit against your actual tax liability at lodgement.

How the two systems compare

Feature	PAYG Withholding	PAYG Instalments
Who it applies to	Employees	Self-employed, investors
Triggered by	Employer paying wages	ATO after first year with investment/business income
Frequency	Each pay run	Quarterly (or monthly for large payers)
Amount calculated by	Employer (from ATO tables)	ATO (from prior year) or taxpayer’s own estimate
Adjustable?	Via TFN declaration or withholding variation	Yes — you can vary the instalment amount
Appears at EOFY as	Tax withheld on income statement	Tax instalments on income statement

Why employees with investment income need both

If you are an employee who also earns rental income, dividends, or interest, your employer’s withholding only covers your employment income. The investment income sits outside the withholding system. The ATO will assess tax on that income when you lodge, and if you have not been paying instalments, the full amount falls due at that point.

Once your investment income passes the ATO’s threshold, the system typically shifts you onto PAYG instalments automatically in the following year. In the first year of significant investment income, the bill at lodgement can be larger than expected.

Common reasons the gap is larger than expected

Multiple jobs. Each employer withholds on their own payments as if it is your only job. When incomes are combined at lodgement, the marginal rate on the higher combined income is greater than what either employer withheld. The more common this is among part-time workers and people with side employment.

HELP debt not disclosed. If you have a HELP debt and did not tick the HELP box on your TFN declaration, your employer is not withholding for the repayment component. The ATO adds the repayment when you lodge based on your repayment income.

Medicare Levy Surcharge. If your income exceeds the MLS threshold and you do not have qualifying private health insurance, the ATO assesses the surcharge at lodgement. Employers do not withhold for MLS unless instructed.

Year-end bonuses. A large bonus paid in the final pay run of the year can push annualised income into a higher bracket, but the withholding tables may not catch up if the bonus is paid separately without annualisation.

How to forecast the shortfall during the year

1. Add your year-to-date gross income across all sources (all jobs, investment income received so far).
2. Run the full-year estimate through the Income Tax Calculator with HELP toggled on if applicable.
3. Add up the total PAYG withheld shown on your payslips, plus any instalments paid.
4. Subtract the total credits from the tax estimate. A positive number is what you still owe; a negative number is your likely refund.

Doing this exercise in April or May gives enough time to act before the end of the financial year.

Fixing the gap before EOFY

Adjust withholding via your employer. You can submit a withholding variation to ask your employer to deduct an extra amount each pay. This is simpler than making voluntary payments and ensures the credit lands correctly on your income statement.

Vary your PAYG instalment. If you are on instalments and expect this year’s income to differ from last year, you can lodge a variation with your BAS or instalment activity statement. Varying downward reduces current cash outflow; varying upward pre-pays more, reducing the year-end bill.

Make a voluntary payment to the ATO. You can send any amount directly to the ATO via BPAY using your instalment account reference. It appears as a credit on your myGov account and will offset against your assessment at lodgement.

Plan for the bill if the gap is unavoidable. If you know a shortfall is coming, setting aside the estimated amount in a high-interest savings account gives you the cash ready when the assessment arrives — and earns interest in the meantime.

How it resolves at lodgement

When you lodge your tax return, the ATO calculates your actual tax liability based on total income, deductions, and offsets. It then subtracts every credit on your account: total PAYG withheld, total instalments paid, and any voluntary payments. If the credits exceed the liability, the difference is refunded. If the liability exceeds the credits, the balance is due on the date shown in the notice of assessment.

PAYG withholding and instalments are both approximations designed to collect tax close to when income is earned. Staying aware of the gap — and adjusting before lodgement — keeps the final reconciliation manageable.

Next payroll step

If you are reconciling withheld tax against real payroll records, move from the estimate into the underlying documents:

• Use the PAYG withholding calculator to check the per-pay estimate
• Build cleaner payroll records in the payroll document hub
• Generate a compliant payslip if you need to recreate or standardise payroll output