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Tax Calculation

warning

Tax amounts must be calculated by applying the tax percentage to the sum of all receipt line totals for that tax type, not by summing per-line tax calculations. Summing per-line taxes introduces rounding differences that will cause validation errors.

When ReceiptLinesTaxInclusive is true​

  • LineTotal values already include tax
  • SalesAmountWithTax = sum of LineTotal for all lines with this tax type
  • TaxAmount = SalesAmountWithTax - round(SalesAmountWithTax / (1 + TaxPercent/100), 2)
  • TotalAmount must equal the sum of all LineTotal values

When ReceiptLinesTaxInclusive is false​

  • LineTotal values are pre-tax amounts
  • TaxAmount = round(sum of LineTotal for this tax type × TaxPercent/100, 2)
  • SalesAmountWithTax = sum of LineTotal for this tax type + TaxAmount
  • TotalAmount must equal the sum of all LineTotal values plus the sum of all TaxAmount values

Rounding​

Rounding uses MidpointRounding.ToEven (banker's rounding) to 2 decimal places.

Totals Cross-Check​

TotalAmount must also equal the sum of all SalesAmountWithTax values across all tax entries.