Identity Services
TFN Validation (Format Check)
Structural checksum validation for Australian Tax File Numbers. Validates format and algorithm — does not perform ATO registry lookups.
Tax File Numbers are sensitive identifiers, and getting the format wrong creates headaches downstream — rejected ATO lodgements, failed payroll processing, and manual data entry rework. Catching invalid TFNs at the point of entry saves time and reduces compliance risk.
The Checkify TFN validation endpoint checks the structural validity of a Tax File Number using the official checksum algorithm. It accepts both 8-digit (older format) and 9-digit TFNs, validates the checksum, and returns the formatted number along with a validity flag.
Important: This is structural validation only. The endpoint confirms that a TFN conforms to the correct format and passes the checksum algorithm. It does not contact the ATO and cannot confirm whether a TFN has actually been issued to a specific person or entity.
Anyone who's run a payroll knows the drill. A new employee fills out their TFN declaration, someone keys it into the system, and two weeks later the ATO rejects the PAYG lodgement because the number was wrong. Now you're chasing the employee for a correction, re-submitting the lodgement, and hoping it doesn't happen with the next batch. Validating the checksum at the point of entry catches the obvious mistakes — transposed digits, missing numbers, and flat-out typos — before they cause real problems.
The algorithm itself is straightforward (weighted digit sum, modulo 11), but the point isn't the maths — it's catching errors at the right moment. A TFN that fails the checksum is almost certainly wrong, and flagging it immediately saves everyone time. For bulk scenarios like payroll migrations or super fund consolidations, upload a CSV and validate thousands of TFNs in one batch. And if you also collect Director IDs, the Director ID validation endpoint works the same way — structural checksum validation, instant response, same bulk processing option.
What you get
Endpoint capabilities and technical details.
Checksum validation
Uses the official TFN checksum algorithm (weighted digit sum, modulo 11) to verify structural validity. A random 9-digit number will almost certainly fail.
8 and 9-digit support
Handles both the older 8-digit format and the current 9-digit format. Both are still in active circulation.
Formatted output
Returns the TFN in standard formatted form (XXX XXX XXX) for consistent storage and display.
Sub-millisecond response
No external service calls — validation runs locally using the checksum algorithm. Responses are instant.
Bulk processing
Upload a CSV of TFNs for batch validation. Useful for payroll onboarding or data migration where you need to verify thousands of records.
Why use this endpoint
Catch errors at the form
Validate TFN format as the user types or on form submission. Reject structurally invalid numbers before they enter your system.
Cleaner payroll data
Pre-validate TFNs during employee onboarding. Reduces rejected ATO lodgements and manual correction cycles.
Data migration confidence
Bulk-validate TFNs when migrating between payroll or HR systems. Flag structurally invalid records before they propagate.
Built for your industry
Common use cases across industries that rely on validated Australian data.
Payroll & HR
Validate employee TFNs during onboarding to prevent rejected PAYG lodgements with the ATO.
Accounting
Verify client TFNs when setting up new tax returns or activity statements.
Financial Services
TFN validation during account opening for investment accounts, superannuation, and managed funds.
Superannuation
Validate member TFNs during fund transfers and consolidation requests.
Trusted data, transparent pricing
TFN validation uses the published checksum algorithm to verify structural format. This endpoint does not contact the Australian Taxation Office and cannot confirm TFN issuance. It should be used as a first-pass data quality check, not as proof of identity.
Source: Checksum algorithm (no external lookup)
Structural validation only. This endpoint checks format and checksum. It does not contact any government registry and cannot confirm whether the identifier has been issued.
How search units work
Checkify uses a simple unit-based model. Each paid API call costs 1–3 search units depending on the endpoint. Your monthly plan includes a set number of units — use them on any endpoint, any time. No hidden fees.
This endpoint: 1 unit per call
1 unit deducted per successful API call.
Ready to integrate?
One REST endpoint, JSON responses, Bearer token auth. No SDK required — just HTTP. Check the full docs for parameters, response schemas, and error codes.
curl -H "Authorization: Bearer ck_prv_..." \ "https://checkify.com.au/api/v1/tfn?tfn=123456782"
{
"tfn": "123456782",
"tfnFormatted": "123 456 782",
"valid": true,
"notice": "Structural validity confirmed. This check does not perform a live ATO registry lookup."
}
Frequently asked questions
Does this confirm the TFN is real?
Why offer this if it doesn't do a live lookup?
Is it safe to send TFNs over the API?
Does it handle both 8 and 9-digit TFNs?
More Identity Services
Other endpoints in this category.
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