SAB Account AI / ATO Verification

PAYG Withholding Verification

Independent verification of PAYG withholding calculations against ATO NAT 1004 published sample data. Verified 25 May 2026 · FY2025-26 Stage 3 rates.

✅

All 5 test cases pass — zero variance

ATO-permitted tolerance: ±$1 per NAT 1004 rounding rules. Actual variance: $0.

Test Results

#	Scenario	Scale	Gross (fn)	Expected	Got	Variance
1	International student	Scale 5	$1,000	$44	$44	$0	✅
2	Australian resident	Scale 2	$2,564	$468	$468	$0	✅
3	Second job (no threshold)	Scale 1	$4,240	$1,226	$1,226	$0	✅
4	Foreign resident (482 visa)	Scale 3	$3,690	$1,106	$1,106	$0	✅
5	High income resident	Scale 2	$5,192	$1,310	$1,310	$0	✅

Integrity Checks

AMedicare not double-counted on Scale 2✅

BScale 5 withholds less than Scale 2 at same income✅

CScale 1 withholds more than Scale 2 at same income✅

DForeign residents (Scale 3) pay $0 Medicare✅

Method

The engine implements the ATO NAT 1004 (Schedule 1) weekly coefficient formula:

Convert period earnings to weekly equivalent: x = floor(earnings / divisor) + 0.99
Locate the correct bracket where x < limit
Apply the formula: weekly = a × x − b
Round the weekly result to the nearest dollar
Scale back to the pay period

LITO is embedded in Scale 2 and Scale 5 coefficients. Medicare levy is embedded in Scale 1 and Scale 2. Monthly pay cycles apply the ATO's 33-cent adjustment before conversion.

Source

ATO NAT 1004: Statement of formulas for calculating amounts to be withheld

ATO Schedule 15: Tax table for working holiday makers (NAT 75331)

ATO sample data: withholding-amounts-sample-data

Stage 3 rates confirmed unchanged for FY2025-26 per ATO, May 2025