How I’m automating monthly IAS / PAYG withholding verification in Xero

This is an in-progress Xero workflow for automating Australian monthly IAS/PAYG withholding verification while retaining human approval and lodgement. One client workflow kept repeating: check payroll, check the Activity Statement, move it through to Xero Tax, get approval and lodge.

It looked like a straightforward automation project. But the more I investigated, the clearer it became that a blind build would be the wrong move.

The project is still in progress, and the goal is deliberately narrow: reduce the repetitive effort of verifying each client’s monthly PAYG withholding position. It is not a system for automatically filing an IAS.

The three checks

IAS means Instalment Activity Statement. This project is focused on monthly PAYG withholding.

The workflow has three explicit checks:

Confirm the previous month’s pay runs are posted.
Read W1 and W2 in the Payroll Activity Summary.
Read W1 and W2 in the Activity Statement.

Only then does it proceed, and only if the figures agree.

Flowchart showing the manual monthly IAS process: confirm payroll runs are complete, compare Payroll Activity Summary and Activity Statement W1 and W2 values, flag issues, then hand off to Xero Tax for human-controlled filing. — The existing process has clear control points: confirm payroll is posted or complete, compare W1 and W2, and investigate any mismatch before the Xero Tax handoff.

For context, W1 is total salary, wages and other payments. W2 is the amount withheld from those payments. The automation needs to respect both numbers, not just the tax total.

The durable route: public API reconstruction

The primary production path is the supported public API because it is the route I can design to be repeatable, monitored and maintained.

For W2, the logic is reasonably direct: select the relevant posted pay runs by payment date and sum their tax totals.

W1 needs more care. A naïve total of every earnings line is not reliable. The workflow needs to retrieve pay items and earnings settings, identify the earnings rates reportable as W1, then aggregate only the relevant payslip earnings lines for each employee and pay run.

That is more deliberate than moving a single report total around, but it makes the calculation explainable. If a result looks wrong, I can trace how it was built.

The research finding that changed the design

During my technical investigation, I also explored the private in-session/UI route. It can surface Xero-calculated Payroll Activity Summary W1 and W2 alongside the Activity Statement W1 and W2 values expected to be filed.

That makes an exact-value comparison possible without line-by-line re-derivation, which is why I am evaluating it as the primary verification check. The public API remains the supported production path; the exploratory comparison is valuable because it tests whether the reconstructed values match the values Xero itself presents.

This research matters because uncommon overtime, deductions, adjustments or special earnings categories can make a simplistic reconstruction diverge unless every classification rule is implemented correctly. I am treating the private route as research, not a deployable foundation: I will not build a workflow that depends on an undocumented interface without first proving that it is reliable, governed and safe to operate.

Diagram comparing a supported public API reconstruction of W1 gross wages and W2 tax withheld with an exploratory private-route exact-value comparison. — The public API is the durable production path. The private-route finding is exploratory research into an exact-value comparison layer, not a deployable unsupported automation.

Flowchart showing a supported public API route and an exploratory private in-session comparison route converging after payroll and Activity Statement checks, then handing off to Xero Tax for human approval and lodgement. — Both routes are being assessed to verify bookkeeping figures and flag mismatches. The handoff to Xero Tax remains a separate human-controlled stage.

Where the automation stops

Once payroll status and both W1/W2 comparisons have passed, the bookkeeping verification is complete. The next steps happen in Xero Tax: import, obtain client approval and e-signature, then lodge. A human remains responsible for that decision and send.

The system should flag missing payroll runs and mismatches for review. It should not assume that every business has the same reporting calendar or automatically file anything. For example, a business with quarterly GST can receive monthly IAS forms for early months and a BAS for the relevant quarterly period.

Building something people can trust

The next step is testing the public-API reconstruction across representative payroll scenarios and documenting the exceptions. The goal is not to make the workflow look clever. It is to make every comparison repeatable, explainable and useful to the person responsible for the next decision.

That is the difference between a quick demo and an automation a firm can rely on each month.

Need help mapping a high-volume workflow without removing its human controls? Book a workflow audit with me.

This article is about workflow design and is not tax, legal or compliance advice. Reporting obligations and circumstances vary; confirm the correct treatment with a qualified Australian tax professional.