Resolving Errors in Stripe Checkout: Trial Subscriptions and Additional Payment Issues

How I Managed a Trial Subscription with an Immediate Extra Fee Using Stripe

In my recent project, where I was setting up an online service, adapting the payment structure to fit our unique business model was quite challenging. We wanted to offer users a trial subscription that included several seats, but also needed the ability to charge immediately if a user added extra seats beyond the trial offer. After some digging and experimentation with Stripe, I found a practical solution.

Initially, my plan was straightforward: set up a trial subscription through Stripe’s Checkout sessions, where users wouldn’t need to enter payment details until the trial ended. However, the twist was adding an immediate charge if they opted for extra seats during their trial period.

Here’s how I went about integrating this – and some bumps I encountered along the way:

Understanding Stripe’s Capabilities

Stripe offers robust APIs to handle various billing models, including subscriptions with trials. Checkout sessions simplify secure payment processes without handling sensitive payment data directly. However, integrating a trial subscription combined with an immediate additional charge for extra seats wasn’t directly supported in the way I expected.

The Roadblock

I tried directly adding the add_invoice_items within the subscription_data parameter in my Checkout session creation code to handle the extra payment for additional seats:

$session = $client->checkout->sessions->create([
    // URL configurations omitted for brevity
    'line_items' => [['price' => $price->id, 'quantity' => 1]],
    'mode' => 'subscription',
    'subscription_data' => [
        'trial_period_days' => 30,
        'add_invoice_items' => [['price' => $extra_seat_price_id, 'quantity' => 1]]
    ],
]);

However, I was met with an error: Received unknown parameter: subscription_data[add_invoice_items]. It turned out this wasn’t a supported approach through the Checkout sessions endpoint.

Finding a Workaround

After more research and a bit of trial and error, I discovered that handling the trial subscription and immediate additional charges effectively required a bit of a workaround. Here’s what I did:

1. Set Up the Initial Trial Subscription:

I created a Stripe Checkout session for the subscription itself, including only the base number of seats within the trial.

1. Immediate Charge for Extra Seats:

For the immediate charge on extra seats, I initiated a separate invoice item. This was done by creating the invoice items immediately after the session creation but before directing users to the Checkout session for payment. It ensured that as soon as they entered their payment details, the extra charges would be processed, despite the subscription itself starting with a trial.

// First, create a checkout session for the subscription with trial
$session = $client->checkout->sessions->create([
    'line_items' => [['price' => $price->id, 'quantity' => 1]],
    'mode' => 'subscription',
    'subscription_data' => ['trial_period_days' => 30],
]);

// Then, add an invoice item for the extra seat(s)
$client->invoiceItems->create([
    'customer' => $customer_id,
    'price' => $extra_seat_price_id,
    'quantity' => $additional_seats,
]);

// Redirect to the session URL for payment
header("Location: " . $session->url);

Final Thoughts

After implementing this two-step approach, users could sign up for a trial subscription, and if they chose extra seats, the additional fee was charged immediately. This solution maintained a smooth user flow and adhered to our need for secure payment handling.

Stripe’s flexibility and comprehensive documentation were invaluable throughout this process. While certain integrations initially seemed daunting, with some persistence and creative thinking, even complex billing models could be accommodated. If you find yourself stuck with Stripe implementations, remember that often, a little ingenuity goes a long way!