Obtain the applicable jurisdictions, rates, effective dates, tax-inclusive or tax-exclusive pricing policy, invoice identifiers and exemption rules from the responsible accounting adviser or authority. Identify which products, domains, addons and other charges are taxable under that policy.

1. Open System Settings and Tax Configuration. Enable Tax Support and save.
2. Enter the company tax identifier and select the approved inclusive or exclusive pricing mode.
3. In Tax Rules, create the required rules with the correct name, country, state and percentage. Review broad rules for unintended overlap with specific locations.
4. Configure the applicable validation and exemption behavior only after confirming the business requirements.
5. Review Advanced Settings, including taxed item types, rounding calculation mode and any compound-tax treatment.
6. Enable tax on each intended product and addon. Enabling tax support alone does not make every product taxable.
7. Test representative customer locations and approved exemption cases in a private environment before the effective date.

Compare the cart, invoice PDF and accounting export for the same test order. Verify the displayed tax identifier, rate, taxable base and total. Differences between per-line and aggregate rounding should be understood by the accounting team rather than corrected by arbitrary manual adjustments.

Schedule the configuration change around the approved effective date and invoice-generation timing. Review existing published invoices separately. WHMCS 9.0 preserves their contents, so use its supported reissue or adjustment workflow where a correction is required.

Check external fixed-amount subscriptions when an invoice total changes. Keep the previous configuration, approval and test examples in the change record. Avoid copying an old tax-rate example or direct invoice-update SQL into production without regard to the current invoice model.

• Correct a WHMCS invoice without losing its audit trail
• Add and maintain currencies in WHMCS
• Resolve duplicate recurring payment subscriptions
• Record and review changes to customer hosting services

• WHMCS tax configuration
• WHMCS: update tax rates
• WHMCS credit and debit notes
• WHMCS: reissue an invoice