For Developers

SendingThx Integration Guide for Merchants

How to add SendingThx delivery notifications and thank-you relays to a custom checkout.

This guide is for a custom checkout built directly on Stripe Payment Intents — where you write your own backend and frontend code and call the SendingThx API yourself. On Shopify? Skip all of this and install the SendingThx Shopify App instead — no code required.

Overview

SendingThx enables you to send delivery notifications and capture thank-you replies via SMS. When a customer purchases a gift, they can opt in to receive SMS notifications when the package arrives — and recipients can reply with a message of gratitude that's relayed straight back to the purchaser.

Cost: $0.50 per gift or package sent. Flat rate covers all SMS — delivery notification to recipient, confirmation to sender, and the recipient's reply if they send one. No monthly fees.

Prerequisites

1Connect Your Stripe Account to SendingThx

  1. Visit sendingthx.com/connect
  2. Click "Connect with Stripe"
  3. Log in to your Stripe account and authorize SendingThx to charge for SMS delivery events
  4. You'll be redirected back to SendingThx — your account is now connected

That's it. SendingThx will charge $0.50 per gift or package sent.

2Add the SMS Consent Widget to Your Checkout

The SMS consent widget collects permission from customers before SendingThx sends them notifications. It's optimized for mobile with a space-efficient design, while keeping all compliance text fully visible.

Add the script tag

In your checkout HTML, add this to the <head> section:

<script src="https://www.sendingthx.com/consent-widget.umd.min.js"></script>

This is hosted directly on sendingthx.com, so it always serves the current version — no separate CDN account or repo access required.

Add the widget container

In your checkout form, add this where you want the consent section to appear:

<div id="sendingthx-consent"></div>

Initialize the widget

After your Stripe Elements initialization, mount the widget:

SendingThxConsent.mount('#sendingthx-consent', {
  onConsent: (data) => {
    // Save consent data to your form
    window.sendingthxConsent = data;
  },
});

The default checkbox text includes full Twilio compliance language (SMS & data rates, HELP/STOP) — no customization needed unless you want shorter labels.

3Wire the Widget into Your Checkout Form

The consent widget is the only additional field you need to add — names are extracted automatically from Stripe's payment data.

Stripe's Payment Element collects: billing name (sender), shipping name and address (recipient).

The consent widget collects: SMS consent checkboxes, phone numbers for sender and recipient, and an optional occasion and gift note.

<form id="checkout-form">
  <!-- Stripe Payment Element (collects payment + shipping details) -->
  <div id="payment-element"></div>

  <!-- SendingThx SMS Consent Widget -->
  <details open>
    <summary>🎁 Add delivery text notifications</summary>
    <div id="sendingthx-consent"></div>
  </details>

  <button type="submit">Complete Purchase</button>
</form>

4Process Payment and Notify SendingThx

When the customer submits the form: confirm the PaymentIntent with Stripe, extract names from Stripe's billing and shipping details, call the SendingThx API with order details and consent data, then redirect to your success page.

Backend example (Node.js)

app.post('/api/checkout', async (req, res) => {
  const {
    paymentIntentId,
    senderConsent, senderPhone,
    recipientConsent, recipientPhone,
    occasion, giftNote,
  } = req.body;

  const paymentIntent = await stripe.paymentIntents.retrieve(paymentIntentId);
  if (paymentIntent.status !== 'succeeded') {
    return res.status(400).json({ error: 'Payment not completed' });
  }

  // Names come from Stripe's billing_details / shipping — see full guide
  // for the parseFullName() helper.

  if (senderConsent && recipientConsent) {
    await fetch('https://api.sendingthx.com/api/v1/orders', {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
        'Authorization': `Bearer ${process.env.SENDINGTHX_API_KEY}`,
      },
      body: JSON.stringify({
        stripe_payment_intent_id: paymentIntentId,
        sender_phone: senderPhone, sender_consent: senderConsent,
        recipient_phone: recipientPhone, recipient_consent: recipientConsent,
        occasion, gift_note: giftNote,
      }),
    });
  }

  res.json({ success: true, redirectUrl: '/success' });
});

Frontend example

document.getElementById('checkout-form').addEventListener('submit', async (e) => {
  e.preventDefault();

  const result = await stripe.confirmPayment({
    elements,
    confirmParams: { return_url: `${window.location.origin}/success` },
    redirect: 'if_required',
  });
  if (result.error) return console.error(result.error);

  const consentData = window.SendingThxConsentData?.() || {};

  const response = await fetch('/api/checkout', {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({
      paymentIntentId: result.paymentIntent.id,
      senderConsent: consentData.senderConsent || false,
      senderPhone: consentData.senderPhone,
      recipientConsent: consentData.recipientConsent || false,
      recipientPhone: consentData.recipientPhone,
      occasion: consentData.occasion,
      giftNote: consentData.giftNote,
    }),
  });

  if (response.ok) window.location.href = '/success';
});

5Verify Your Integration

Test SMS delivery

  1. Complete a test purchase through your checkout
  2. Use a test phone number (SendingThx allows Twilio test numbers)
  3. Wait 1–3 minutes for the SMS to arrive in test mode
  4. Confirm the message content matches your recipient's phone

Check usage and billing

Log in to sendingthx.com/dashboard → Usage & Billing to confirm the test event is listed. The $0.50 charge appears as a Stripe invoice on your next billing cycle — check Invoices in your Stripe Dashboard.

Configuration

From sendingthx.com/dashboard, under Settings, you can enable or disable the gifter-reply relay and view the Twilio compliance language included in every message. Under Integrations, you'll find your SendingThx API key — treat it like a password, keep it out of client-side code, and rotate it if it's ever exposed.

Troubleshooting

SMS not received — verify the recipient phone is in E.164 format (+1 country code plus 10 digits), confirm the order shows up in your SendingThx dashboard.

Stripe Connect authorization failed — make sure you completed the OAuth flow at sendingthx.com/connect and that your Stripe account is in live mode, then try disconnecting and reconnecting.

API key error — copy the full key from the dashboard with no extra spaces, and check your Authorization header reads Bearer {key}.

Consent widget not showing — make sure the script tag is in <head> before your checkout code runs, check the browser console for errors, and confirm the #sendingthx-consent div exists in your HTML.

Support

Questions about your integration can go to support@sendingthx.com.

Connect your Stripe account →