Finance & Compliance
GST Invoice & HSN Compliance Kit
Offline, deterministic 8-stage GST invoice auditor with checksum verification and CA handoff pack.
Your invoice totals can add up and still be completely wrong. A GSTIN checksum with one typo, an intra-state CGST/SGST split on an inter-state sale, missing HSN depth based on turnover bands, or a duplicate invoice number in your export will trigger GSTR-1 mismatches and buyer payment rejections.
An offline, deterministic statutory audit engine that verifies GST invoice JSON across 8 stages and generates a severity-ranked CA handoff pack.
Indian SMB sellers, D2C brands, freelancers, tech agencies invoicing B2B clients, and chartered accountants reviewing sales data.
Mathematical GSTIN mod-36 checksum, AATO-based HSN depth validation (4 vs 6 digits), supply-place tax split, and e-invoice gates.
33 passing automated tests, under 3-minute execution, 100% offline without accounting software or API keys.
Why this architecture wins
| Without this skill (Manual & Flawed) | With this skill (Deterministic & Gated) |
|---|---|
| ✕ Invoices rejected by clients or GSTR-1 portals due to invalid GSTIN check digits or tax split errors. | ✓ Pre-issue 8-stage audit verifying checksums, tax splits, and HSN depths with zero portal delay. |
| ✕ Scattered billing exports resulting in expensive CA reconciliation charges. | ✓ Instant 6-file CA handoff pack (audit.json, batch.md, fix-list.md, ca-questions.md). |
| ✕ Missing mandatory B2B e-invoicing for turnover above ₹5 Cr leading to compliance penalties. | ✓ Automated e-invoice gate enforcing IRN, ACK, and QR presence based on turnover threshold. |
What's inside
- ✓skills/gst-invoice-compliance-kit/SKILL.md (8 statutory stages & rule reference)
- ✓audit-invoice.mjs (Single-invoice auditor with strict CI exit codes)
- ✓batch-audit.mjs (Batch auditor with duplicate invoice detection)
- ✓hsn-lookup.mjs (HSN/SAC depth orientation by AATO turnover band)
- ✓Checksum verification for 15-character statutory GSTIN structure
- ✓CA handoff pack generator (audit.json, batch.md, fix-list.md, ca-questions.md)
Built with
- Node.js
- GST Law & Rules
- HSN/SAC Codes
- E-Invoice IRP
- E-Way Bill
- CI Gates
How to use this skill (Step-by-step)
Run offline in your local workspace, orchestrate through any agent (Claude Code, Cursor, Antigravity, Cline), or plug directly into CI/CD pipelines.
Extract the Compliance Kit
Unpack the audit scripts into your local billing system or finance repository.
unzip gst-invoice-compliance-kit-1.0.0.zip -d ./gst-toolsExport Invoice Data to JSON
Format your invoice data according to the clean JSON fixture schema.
cat ./gst-tools/examples/invoice.clean.jsonAudit Invoice Against Statutory Rules
Run the single-invoice auditor with strict CI exit codes.
node ./gst-tools/scripts/audit-invoice.mjs ./invoice.json --strictGenerate CA Handoff Pack for Batch Invoices
Produce audit.json, batch.md, and ca-questions.md for your CA before filing.
node ./gst-tools/scripts/batch-audit.mjs ./batch.json --out=./ca-packIncluded with every purchase
- Instant download with commercial license for personal & client billing
- All 4 standalone scripts requiring zero npm dependencies
- Full test suite with 33 passing automated tests
- Clean, broken, and batch test fixtures with golden audit reports
- 12 months of free v1.x statutory updates
- 30-day money-back satisfaction guarantee
Questions
Do I need accounting software or internet access to run this?
No. The engine runs 100% locally on your machine or in your CI/CD billing pipeline with zero network calls, API keys, or monthly subscriptions.
Does it verify e-invoice and e-way bill rules?
Yes. It enforces mandatory B2B e-invoicing for turnover above ₹5 Crore (IRN, ACK, QR) and e-way bill applicability for goods consignments above ₹50,000.
Is this legal or tax advice?
No. It is a deterministic data-quality gate based on statutory GST rules that flags discrepancies so you can fix them before filing or submitting to your CA.