Guidelines for interfacing Indian payment gateways with e-invoicing systems

I. Overview of India's payments ecosystem

India's digital payments market has shown explosive growth in recent years, with the Unified Payment Interface (UPI) becoming the dominant payment method. in 2022, the volume of UPI transactions surpassed 74 billion, totalling Rs. 126 trillion. This rapid development has created favourable conditions for the deep integration of e-invoicing systems and payment channels.

Driven by the GST tax reforms, India's electronic invoicing (e-Invoice) system has been made progressively mandatory since 2020. It is currently applicable to businesses with an annual turnover of Rs 20 million or more. The threshold is expected to come down to Rs 10 million by the end of 2023.

II. Core docking technology programme

1. API integration model

• Real-Time Synchronisation Interface: Instant transfer of transaction data via RESTful APIs
• Batch Processing Interface: Timed data exchange suitable for large-value B2B transactions
• Webhook callback mechanism: Asynchronous notification of processing results

2. Data standardisation

Must conform to the JSON Schema as specified by IRP (Invoice Registration Portal):

{

  "Version": "1.1",

  "TranDtls": {

    "TaxSch": "GST".

    "SupTyp": "B2B".

    ...

}

3. Security certification requirements

• GSTIN number verification (15 characters)
• IRN (Invoice Reference Number) Generation Rules
• DSC (Digital Signature Certificate) digital signature

III. Detailed implementation steps

Stage I: Pre-preparation (takes about 7 working days)

1. Qualification
   • GST Portal Register Account to Apply API Key
   • PCI DSS Compliance Certification (platform for memory card data)

2.Environment Configuration

• Sandbox test environment setup
• IP Whitelist Setting

3.Preparation of development resources

• Java/Python SDK Integration Package Download
• Postman Test Collection Import

Stage 2: Technical interface (development cycle 10-15 days)

A. Positive Process Realisation

[Merchant System] → [Generate Order] → [Call PayAPI] → [Return to PaymentLink]

          ↓ ↑  

[User Payment] ← [Show QR/UPIID] |

          ↓ |  

[Success Callback] → [Trigger e-Invoicing] → [IRP Registration]

B. Reverse process handling

[Refund request] → [Return funds in the same way]

      ↓  

[GenerateCreditNote] → [IRP Filing]

C. Exception scenario response programme

IV. Key considerations

Timeliness requirements:
- UPI transactions need to be invoiced within 24 hours
- B2G transactions must be uploaded to the e-Invoice portal within 48 hours

Special Business Scenarios:
✔️ Cross-border transactions require an additional FIRC number
✔️OEM OEM need to indicate Principal-GSTIN

Performance Optimisation Recommendations:
▶︎ HSN coding for high-frequency queries using Redis caching
▶︎ uses Kafka to handle enterprise-class traffic of 100,000+ tickets per day

V. Tracking of latest policy developments

Q2 2023 Update Highlights.
✓ QRMP programme to simplify quarterly filing for small and medium-sized merchants
✓ E-Way Bill and e-Invoice auto-association function is online

Prevention of common audit problems.
⚠️ GSTINs with no transactions for 12 consecutive months may be suspended
⚠️ Duplicate submission of the same IRN will result in a penalty of Rs. 5,000

Typical Success Stories Reference.
▸ Swiggy automates the entire order→payment→invoicing chain (TPS boost of 300%)
▸ Zomato shortens settlement cycle by pre-generating IRNs 40%

O&M Monitoring Metrics Recommendation.
✅ Daily reconciliation variance rate < 0.01%
✅ Average monthly API response time ≤ 800ms

This article is continually updated to 15 August 2023, the date of the tax authority's circular.

VI. Deep docking solutions

1. Multi-payment channel integration strategy

Diverse payment methods exist in the Indian market and a successful docking solution needs to be compatible:

• UPI Ecosystem(76% share of mobile payments)
  • PSP Support List: PhonePe, Google Pay, Paytm
  • VPA (Virtual Payment Address) specification checking
• Traditional banking channels
  • NEFT/RTGS large clearing
  • IMPS Instant Transfer Limit Adjustment (Currently up to Rs 20,000 per single transaction)
• International Card Organisation
  3DS2.0 certification process optimisation
  Local acquiring routing (HDFC/Axis etc. acquiring lines)

2. GST Compliance Enhancement Programme

HSN/SAC Code Intelligent Matching System

def auto_match_hsn(product_desc).

    # NLP processing of commodity description text 

    from sklearn.feature_extraction.text import TfidfVectorizer  

    # Load the official coding library published by CBIC  

    return top3_matching_codes 

TCS/TDS withholding module design principles:

• B2C e-commerce applies 1% TCS levy point setting
• B2B services need to differentiate between clauses 194J/194H

VII. Technical architecture best practices

Comparison of microservices deployment options

Disaster recovery mechanisms

Data Synchronisation Dual-Activity Architecture:
Mumbai Main Centre ↔︎ Hyderabad Disaster Recovery Centre
✔️ MySQL Group Replication guarantees RPO <5 seconds
✔️ S3 Storing PDF Copies of Tickets Across Regions

Meltdown Degradation Programme:
▸ RocketMQ Stacking Alerts Trigger Manual Review Queues
▸ UPI failure automatically switches to Net Banking

VIII. Cost optimisation guidelines

Cost structure analysis (100,000 transactions/month as an example)

O&M manpower reference

-Junior Developer: Handle daily exception monitoring (3 person shift system)
-Senior Architect: responsible for quarterly GST rule upgrades (1 person)

IX. Future directions for evolution

Predicted Technology Trends 2024.
🚀 Embedded Finance (Embedded Finance) and ERP deep integration
🌐 CBDC Digital Currency Pilot Access Preparation
🔍 AI audit bots automatically identify GSTR discrepancies

Industry Recommendation Adoption Index.
★★★★☆First-mover advantage enterprises should layout offline invoice agreement in advance
★★★★☆☆ Small and medium-sized merchants can wait and see the effect of QRMP simplification policy

This technical whitepaper is produced by the [your company name] Payment Research Institute, for a full version of the implementation please contact the team of professional consultants. Latest revised version number v2023.08, please retain the source statement.