Subscription billing with Inzi

Accept recurring crypto payments for your SaaS product using Inzi payment links and metadata tracking.

Automatic recurring charges are not yet supported. Use payment links with metadata to track subscriptions manually.

Create a payment link for each plan


curl -X POST https://api.inzilink.com/api/v1/links \
  -H "Authorization: Bearer sk_live_xxxxx" \
  -H "Content-Type: application/json" \
  -d '{
    "title": "Pro Plan — Monthly",
    "amount": "29.00",
    "currency": "USD",
    "type": "subscription",
    "metadata": { "plan": "pro", "interval": "monthly" }
  }'

Embed the payment link URL on your pricing page or send it directly to customers:


<a href="https://inzilink.com/p/your-link-code" class="btn">
  Pay with Crypto — $29/mo
</a>

Track payments via metadata

Each payment through the link creates a checkout. Include user_id in metadata by creating individual checkouts:


const checkout = await fetch('https://api.inzilink.com/api/v1/checkouts', {
  method: 'POST',
  headers: {
    'Authorization': `Bearer ${process.env.INZI_API_KEY}`,
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    amount: '29.00',
    currency: 'USD',
    description: 'Pro Plan — Monthly',
    metadata: {
      user_id: userId,
      plan: 'pro',
      interval: 'monthly',
      billing_period: '2026-04',
    },
    redirect_url: `https://yourapp.com/billing/success`,
    webhook_url: 'https://yourapp.com/webhooks/inzi',
  }),
})

Handle subscription webhooks


app.post('/webhooks/inzi', async (req, res) => {
  const event = verifyWebhook(req.body, req.headers, WEBHOOK_SECRET)
 
  if (event.event === 'checkout.completed') {
    const { user_id, plan, billing_period } = event.data.metadata
 
    // Extend subscription
    await extendSubscription(user_id, plan, billing_period)
 
    // Send receipt
    await sendSubscriptionReceipt(user_id, event.data.amount)
  }
 
  res.json({ ok: true })
})

Send renewal reminders

Since auto-charge isn’t available yet, send reminders when subscriptions are expiring:


// Cron job: check for expiring subscriptions daily
const expiring = await getExpiringSubscriptions()
 
for (const sub of expiring) {
  // Create a new checkout for renewal
  const checkout = await createCheckout({
    amount: sub.plan_price,
    metadata: { user_id: sub.user_id, plan: sub.plan, type: 'renewal' },
  })
 
  await sendRenewalEmail(sub.user_id, checkout.checkout_url)
}

Recommended approach

Create checkouts per user (not shared payment links) so metadata tracks who paid
Store billing_period in metadata for reconciliation
Use webhooks to auto-extend subscriptions
Send renewal links via email/in-app notification before expiry