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Overview

InventPay supports two types of payment requests, each designed for different use cases. Understanding when to use each type will help you create the best payment experience for your customers.

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Payment Types

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Fixed Currency Payment

A Fixed Currency Payment generates an immediate payment address for a specific cryptocurrency. The customer must pay using that exact cryptocurrency. When to use:
  • You want to accept only a specific cryptocurrency
  • You need an immediate payment address
  • You’re integrating with a system that only supports one crypto type
  • You want to minimize customer confusion by showing only one payment option
Example: 
{
  "amount": 29.99,
  "amountCurrency": "USD",
  "currency": "USDT_BEP20",
  "orderId": "order-12345"
}
Result:
  • Immediate wallet address: 0x742d35Cc6634C0532925a3b844Bc9e7595f0bEb
  • Fixed amount in crypto: 29.99 USDT
  • Customer must pay with USDT on BEP20 network

Create Fixed Payment

View the Create Payment API endpoint

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Multi-Currency Invoice

A Multi-Currency Invoice lets customers choose which cryptocurrency they want to pay with. InventPay displays conversion rates for all supported cryptocurrencies. When to use:
  • You want to maximize payment flexibility
  • Your customers use different cryptocurrencies
  • You want to increase conversion rates by offering choices
  • You’re running a consumer-facing application
Example: 
{
  "amount": 49.99,
  "amountCurrency": "USD",
  "orderId": "order-67890"
}
Result:
  • Invoice URL with currency selector
  • Conversion rates for: BTC, ETH, LTC, USDT_ERC20, USDT_BEP20
  • Customer selects their preferred cryptocurrency
  • Unique address generated after selection

Create Invoice

View the Create Invoice API endpoint

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Payment Lifecycle

Every payment goes through a series of states from creation to completion:

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Payment States

Initial State: Payment is waiting for funds to arrive
  • Payment address has been generated
  • Customer needs to send cryptocurrency
  • No funds received yet, or insufficient funds
  • Awaiting blockchain confirmations
Actions:
  • Display payment address to customer
  • Show QR code for mobile wallets
  • Monitor for incoming transactions
Final State: Payment successfully received and confirmed - Full payment amount received - Required confirmations reached - Funds available in your balance - Order can be fulfilled Actions: - Fulfill the order - Send confirmation to customer - Update your database
Final State: Payment window closed without receiving payment - Expiration time reached - No payment or partial payment received - Payment address no longer monitored Actions: - Cancel the order - Create new payment if customer still wants to pay - Notify customer of expiration
Final State: Payment encountered an error
  • Technical error during processing
  • Invalid transaction detected
  • Blockchain issues
Actions:
  • Contact support if error persists
  • Create new payment for customer

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Unique Payment Addresses

Every payment request generates a unique wallet address for security and tracking purposes.

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Benefits

Enhanced Security

Each address is used only once, preventing address reuse attacks

Easy Tracking

Instantly match incoming payments to specific orders

Privacy

Customers’ payment activity remains private and isolated

Auto-Reconciliation

Automatic payment matching eliminates manual reconciliation

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How It Works

  1. Customer initiates checkout → You create a payment request
  2. InventPay generates unique address → Specific to this transaction
  3. Customer sends crypto → To the unique address
  4. InventPay monitors blockchain → Tracks confirmations in real-time
  5. Payment confirmed → Funds swept to your master wallet

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Payment Expiration

All payments have an expiration time to prevent indefinite address monitoring.

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Default Expiration

  • Fixed Payments: 30 minutes
  • Invoices: 60 minutes

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Custom Expiration

You can set custom expiration times between 5 and 1440 minutes (24 hours): 
{
  "amount": 100,
  "currency": "BTC",
  "expirationMinutes": 120 // 2 hours
}
After expiration, payments sent to the address will not be credited. Always create a new payment if the customer still wants to pay.

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Why Payments Expire

  • Resource Management: Monitoring addresses indefinitely is resource-intensive
  • Price Protection: Cryptocurrency prices fluctuate; expiration ensures rate accuracy
  • Abandoned Carts: Prevents cluttering your system with abandoned payments
  • Customer Experience: Creates urgency and reduces confusion

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Partial Payments

InventPay detects when a customer sends less than the required amount.

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Underpayment Detection

If a customer sends less than 95% of the required amount:
  1. Payment status becomes PENDING with underpaid flag
  2. Webhook notification sent: payment.underpaid
  3. Remaining amount calculated and displayed
  4. Customer can send additional payment to same address
Example: 
{
  "status": "PENDING",
  "requiredAmount": "100.00",
  "currentBalance": "90.00",
  "remainingAmount": "10.00",
  "paidPercentage": 90
}

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Handling Underpayments

1

Notify Customer

Inform them of the remaining amount needed
2

Allow Additional Payment

Same address can receive top-up payment before expiration
3

Set Deadline

Communicate expiration time clearly
4

Handle Expiration

If expired with underpayment, decide whether to accept partial payment or refund
If a payment expires while underpaid, contact support to discuss refund or manual completion options.

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Overpayments

If a customer sends more than required, the entire amount is credited to your account. Example:
  • Required: 0.001 BTC
  • Customer sends: 0.0012 BTC
  • Result: Full 0.0012 BTC credited to your balance
Overpayments are kept by the merchant. Consider your refund policy for significant overpayments.

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Blockchain Confirmations

Different cryptocurrencies require different confirmation counts before payment completion.
CryptocurrencyRequired ConfirmationsAverage Time
Bitcoin (BTC)3 confirmations~30 minutes
Ethereum (ETH)12 confirmations~3 minutes
Litecoin (LTC)6 confirmations~15 minutes
USDT (ERC-20)12 confirmations~3 minutes
USDT (BEP-20)15 confirmations~45 seconds
Times are estimates. Network congestion and gas prices can affect actual confirmation times.

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Best Practices

  • Use Fixed Payments for B2B or when you need a specific crypto
  • Use Invoices for consumer applications to maximize flexibility
  • Quick checkouts: 15-30 minutes - Normal purchases: 30-60 minutes - High-value B2B: 2-4 hours
  • Plan for underpayments - Have a refund policy for overpayments - Handle expired payments gracefully
  • Never poll for status updates - Implement real-time webhook notifications - Verify webhook signatures
  • Show exact amount to send
  • Display correct network (ERC-20 vs BEP-20)
  • Include expiration timer
  • Provide QR code for mobile wallets

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Testing Payments

InventPay provides a test mode for development and testing.

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Test Mode Features

  • Separate test API keys
  • No real cryptocurrency transactions
  • Simulate payment confirmations
  • Test webhook deliveries

Get Test API Key

Get your test API key from the dashboard

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Next Steps

Create Payment

Learn how to create fixed-currency payments

Create Invoice

Learn how to create multi-currency invoices

Payment Status

Learn how to check payment status

Webhooks

Set up real-time payment notifications