How to start a stripe subscription with the first 2 months' prorated initial payment upfront

Question

I'm building a checkout page where users sign up for a $100/month product. However, when users sign up, they must pay for the first two months upfront, which must be prorated over time. After the first 2 months, we will ask them to pay 100 USD per month. For example:

• Users who register on January 3, 2024, they will have to pay (3-31)/31) * 100 USD for the remaining 28 days of month 1 and 100 USD for the second month.
• Starting March 1, 2024, they will pay $100 at the beginning of each month to use

I've seen about subscription schedules, but I don't know how to configure the phase to meet the above requirements.

I tried with the solution in here. How to implement stripe subscription with three months initial upfront payment But it cannot be calculated based on the first month's time rate.

Answer 1

Step 0 : Create a Test Clock and/or Customer if necessary

const testClock = await stripe.testHelpers.testClocks.create({
    frozen_time: Math.floor(+new Date() / 1000),
  });

  const customer = await stripe.customers.create({
    description: 'test clock customer',
    email : '[email protected]',
    test_clock: testClock.id,
    payment_method: 'pm_card_amex_threeDSecureNotSupported',
    invoice_settings : {
      default_payment_method : 'pm_card_amex_threeDSecureNotSupported'
    }
  });

Step 1 : Create a Subscription with a 2-month Price, and billing_cycle_anchor set to March 1, 2024

  const subscription = await stripe.subscriptions.create({
    customer: customer.id,
    items: [
      {price:'price_A'} // USD $200 for 2 months
    ],
    payment_behavior : 'allow_incomplete',
    billing_cycle_anchor : 1709251200 // 1 Mar 2024
  }
  );

  console.log(subscription);

Step 2 : Upon successful Subscription first payment, you would create a SubscriptionSchedule for the Subscription

  const schedule = await stripe.subscriptionSchedules.create({
    from_subscription: subscription.id,
  });
  
console.log(schedule);

Step 3 : Update the SubscriptionSchedule to change to a 1-month Price on March 1, 2024

const subscriptionSchedule = await stripe.subscriptionSchedules.update(
    schedule.id, {
      phases:[
        {
          start_date : schedule.phases[0].start_date,
          end_date : schedule.phases[0].end_date,
          items: [{
            price: 'price_A' // USD $200 for 2 months
          }]
        },
        {
          items: [{
            price: 'price_B' // USD $100 for 1 months
          }]
        }
      ]
    }
    );
    
    console.log(subscriptionSchedule);

Advance the test clock to see how it charges