[P2 MEDIUM] SAC Code Misclassification — ITC Trail Inaccuracy

[teetangh]

Summary

The default HSN/SAC code is hardcoded to 999293 ("Consulting services") throughout the codebase. The correct SAC for "Information Technology Consultancy Services" is 998311 or 998399. While rates are unaffected (zero-rated exports), this misclassification causes ITC trail inaccuracies in GSTR-2B.

Priority: P2 MEDIUM

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What's Affected

• lib/compliance/gst.ts — DEFAULT_HSN_SAC_CODE = '999293'
• lib/api/organizations/invoices.ts — DEFAULT_HSN_SAC_CODE = '999293'
• lib/payments/invoicing/invoice-service.ts — DEFAULT_HSN_SAC_CODE = '999293'
• jobs/compliance/gstr8-draft-export.ts — SAC_CONSULTING = '999293'

Correct Codes

• 998311 — Information Technology Consultancy Services
• 998399 — Other Information Technology Services n.e.c.

Impact

• ITC trail inaccuracy — GSTR-2B auto-population may mismatch
• No rate impact — zero-rated exports don't depend on HSN/SAC for tax calculation
• Reporting inaccuracy — GSTR-1 HSN-wise summary will show wrong SAC

Fix

1. Change default SAC to 998311 (or 998399 if more appropriate)
2. Consider making SAC configurable per organization/program
3. Run a one-time migration to update existing invoices

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Related: Part of Organizational Finance Deep Dive (2026-09-03). See bugs/financial-audit/10-org-finance-deep-dive.md.