Compute invoice tax and totals instead of hardcoding taxAmount to zero

[RUKAYAT-CODER]

Overview

InvoicesService.generateAndArchiveInvoice() creates every invoice with taxAmount: 0 and totalAmount: payment.amount, so the total is always identical to the net amount and no tax is ever recorded. The Invoice entity models amount, taxAmount, and totalAmount as three separate decimal columns precisely because they are meant to differ. For any jurisdiction where VAT, GST, or sales tax applies, the archived invoice is not a valid tax document, and the revenue recognition report in ReportingService that reads these columns understates the tax liability to zero.

Specifications

Features:

• Tax is computed from the customer's jurisdiction and the applicable rate.
• totalAmount equals amount plus taxAmount by construction.
• The tax rate and jurisdiction applied are recorded on the invoice.

Tasks:

• Introduce a tax resolution step keyed on the customer's billing country/region, sourced from the payment or user profile.
• Compute taxAmount with decimal-safe arithmetic and set totalAmount = amount + taxAmount.
• Persist the applied rate and jurisdiction in the invoice items or a dedicated column for audit purposes.
• Render the tax line in the generated invoice document.
• Add unit tests for a zero-rate jurisdiction, a standard-rate jurisdiction, and a rounding boundary.

Impacted Files:

• src/payments/invoices/invoices.service.ts
• src/payments/entities/invoice.entity.ts
• src/payments/reporting/reporting.service.ts

Acceptance Criteria

• An invoice for a taxable jurisdiction carries a non-zero taxAmount.
• totalAmount always equals amount + taxAmount.
• The applied rate is recoverable from the stored invoice.
• Revenue reporting reflects the recorded tax.

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Congratulations, @Menjay7! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on July 30, 2026.

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