Implement subscription tax calculation and remittance system

[Smartdevs17]

Description

Automate sales tax/VAT calculation for subscriptions based on customer location, with automated remittance reporting.

Acceptance Criteria

• Tax rate lookup by jurisdiction (country, state/province, city)
• Tax-exempt customer handling (with certificate validation)
• Tax calculation on subscription invoices
• Tax remittance report generation
• Multi-jurisdiction tax support (VAT, GST, sales tax)
• Tax rate change handling for existing subscriptions

Technical Scope

• backend/services/
• src/types/invoice.ts
• contracts/invoice/src/lib.rs
• Edge: nexus determination, tax rate change mid-cycle, digital goods tax classification

[Junman140]

@Junman140 has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

I would want to work on this project because ive being contributing to pi network and stellar for 6 years now and i use mainly typescript, rust and javascript

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Junman140 to this issue.

[drips-wave]

Congratulations, @Junman140! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 2, 2026.

🧑‍💻 @Junman140: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

Warning

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[drips-wave]

This issue has been completed by @Junman140 as part of the Stellar Wave Program's 5th Wave 🥳

😎 @Junman140: You earned 200 Points for completing this issue! After the current Wave ends, you'll be eligible for a percentage of the Wave's reward pool based on the percentage of total points you've earned. Learn more here. You can also Leave a review to share your experience working on this issue.

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