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Overview

You may want to grant usage credits to customers even before they make a purchase. This is useful for:
  • Free trial credits - Give new signups free credits to try your service
  • Promotional campaigns - Grant credits as part of marketing initiatives
  • Testing and demos - Provide credits for product demonstrations
This guide shows you how to grant credits to customers who don’t have an active subscription or purchase yet.

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How It Works

To grant credits before a purchase, you need to:
  1. Create a customer in Polar (if they don’t exist)
  2. Create a meter with Sum aggregation to track usage
  3. Ingest an event with a negative value to grant credits
Why negative values?When you ingest an event with a negative value (e.g., -10) to a meter using Sum aggregation, it grants the customer credits. A negative balance means available credits, which get reduced as they use your service.

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Step 1: Create a Meter

First, create a meter that will track your customers’ usage.
1

Navigate to Meters

In the Polar dashboard sidebar, click on Products > Meters.
2

Create a new meter

Click Create Meter and configure:
  • Name: Give your meter a descriptive name (e.g., “API Calls” or “Storage Usage”)
  • Filter: Add filters to match your usage events (e.g., name equals “api_usage”)
  • Aggregation: Select Sum and enter the property to sum (e.g., units)
The meter must use Sum aggregation for this approach to work.
3

Save the meter

Save your meter and note down the meter name - you’ll need this when ingesting events.
Learn more about creating meters.

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Step 2: Create a Customer

If your customer doesn’t already exist in Polar, you need to create them first.

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Option A: Create via Dashboard

1

Navigate to Customers

In the Polar dashboard sidebar, click on Customers.
2

Add new customer

Click Add Customer and fill in:
  • Email: Customer’s email address (required)
  • Name: Customer’s full name (optional)
  • External ID: Your internal user ID for easy reference (optional but recommended)
3

Save customer

Click Save and note down the Customer ID.

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Option B: Create via API

Use the Polar SDK or API to create a customer programmatically:
create-customer.ts
import { Polar } from "@polar-sh/sdk";

const polar = new Polar({
  accessToken: process.env.POLAR_ACCESS_TOKEN,
});

// Create a new customer
await polar.customers.create({
  email: "[email protected]",
  name: "John Doe",
  externalId: "user_123", // Your internal user ID (optional)
});
Use the externalId field to link Polar customers with your internal user system. This allows you to reference customers without storing Polar’s internal ID.

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Using External ID

If you set an externalId when creating the customer, you can use it in event ingestion instead of the Polar customer ID: 
// Instead of using customerId, use externalCustomerId
await polar.events.ingest({
  events: [{
    name: "api_usage",
    externalCustomerId: "user_123", // Your internal ID
    metadata: { units: -10 }
  }]
});
Learn more about customer management.

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Step 3: Grant Credits by Ingesting a Negative Event

Now that you have a customer and a meter, grant credits by ingesting an event with a negative value.

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Using the Polar SDK

grant-credits.ts
import { Polar } from "@polar-sh/sdk";

const polar = new Polar({
  accessToken: process.env.POLAR_ACCESS_TOKEN,
});

async function grantCredits(customerId: string, credits: number) {
  await polar.events.ingest({
    events: [
      {
        customerId,
        name: "api_usage", // Must match your meter's filter name
        metadata: {
          units: -credits, // Negative value grants credits
        },
      },
    ],
  });
  
  console.log(`Granted ${credits} credits to customer ${customerId}`);
}

// Grant 10 credits to a customer
await grantCredits("cus_abc123", 10);

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Using External Customer ID

If you’re using externalId for customer management:
grant-credits-external.ts
import { Polar } from "@polar-sh/sdk";

const polar = new Polar({
  accessToken: process.env.POLAR_ACCESS_TOKEN,
});

async function grantCreditsToExternalUser(externalUserId: string, credits: number) {
  await polar.events.ingest({
    events: [
      {
        name: "api_usage", // Must match your meter's filter name
        externalCustomerId: externalUserId, // Use your internal ID
        metadata: {
          units: -credits, // Negative value grants credits
        },
      },
    ],
  });
  
  console.log(`Granted ${credits} credits to user ${externalUserId}`);
}

// Grant 10 credits using your internal user ID
await grantCreditsToExternalUser("user_123", 10);

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Step 4: Verify Credits Were Granted

Check that the credits were successfully granted to the customer.

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Using Customer Meters API

import { Polar } from "@polar-sh/sdk";

const polar = new Polar({
  accessToken: process.env.POLAR_ACCESS_TOKEN,
});

// Check customer's meter balance
const meters = await polar.customerMeters.list({
  customerId: "cus_abc123",
});

meters.items.filter((balance) => balance > 0).forEach((meter) => {
  console.log(`${Math.abs(meter.balance)} credits available for ${meter.meter_id}.`);
});

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Example Usage Flow

// Initial state: Customer created, 0 balance
// Grant 10 credits: balance = 10

// Customer uses 3 units
await polar.events.ingest({
  events: [{
    name: "api_usage",
    customerId: "cus_abc123",
    metadata: { units: 3 } // Positive value for usage
  }]
});

// Balance is now 7 (7 credits remaining)

// Customer uses 8 more units
await polar.events.ingest({
  events: [{
    name: "api_usage",
    customerId: "cus_abc123",
    metadata: { units: 8 }
  }]
});

// Balance is now -1 (used 1 unit beyond credits)