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1. Overview & European Payment Architecture

The Gravity Forms Mollie Integration Add-on connects your WordPress forms directly with Mollie, the leading European payment service provider. Mollie empowers businesses across the European Union, the United Kingdom, and international markets to collect funds using localized payment methods that European consumers trust.

Rather than relying solely on international credit cards—which suffer from elevated drop-off rates in key European economies—Mollie unlocks native support for iDEAL (dominant in the Netherlands), Bancontact (standard across Belgium), Sofort/Klarna (Germany and Austria), EPS, Giropay, SEPA Direct Debit, and Cartes Bancaires (France), alongside Visa, Mastercard, American Express, Apple Pay, and PayPal.

2. Mollie Dashboard Setup & API Authentication

Connecting Gravity Forms to Mollie requires obtaining your secure API keys from the Mollie Control Panel.

1. Log in to your Mollie Dashboard.
2. Navigate to Developers → API keys in the left sidebar menu.
3. Mollie provides two distinct API keys:
   • Test API Key: Starts with test_... for staging simulations and checkout testing.
   • Live API Key: Starts with live_... for actual monetary settlements.
4. In WordPress, navigate to Forms → Settings → Mollie.
5. Paste your API Key into the password field. The add-on dynamically determines whether the key is in test mode or live mode based on the prefix.
6. Click Save Settings. The add-on immediately pings the Mollie v2 API to validate account standing and retrieve your enabled payment methods.

3. Feed Configuration & Payment Method Customization

Configure payment feeds inside your forms to control currency mapping, transaction descriptions, and checkout redirection.

Configuring a Mollie Feed

1. Open your target form in Gravity Forms and go to Settings → Mollie.
2. Click Add New to generate a feed.
3. Assign a clear Feed Name (e.g. European Euro Order Feed).
4. Currency Configuration: Set your processing currency (e.g. EUR, GBP, CHF, PLN, or USD). Note that specific local payment methods like iDEAL require transactions to be denominated in EUR.
5. Amount Field Mapping: Select Form Total or map an individual calculated pricing field.
6. Customer Information: Map customer Name and Email address. Mollie uses customer email to send official payment confirmations and localized VAT receipts.
7. Webhook Delivery: Mollie communicates asynchronously with WordPress via background webhooks. The add-on automatically constructs and registers the secure webhook URL on each transaction initiation.

4. Advanced European Workflows & Conditional Routing

Optimize conversion rates across multiple European member states by implementing intelligent localized routing:

• Geo-Targeted Payment Feeds: Create separate Mollie feeds conditioned on the respondent’s Billing Country field. For Dutch visitors (Country is Netherlands), set domestic EUR currency and tailor notifications in Dutch. For UK customers, route to a feed denominated in GBP.
• Dual Gateway Switcher: Enable conditional logic to offer customers a choice between Mollie (for European payment methods like iDEAL and Bancontact) and Stripe or PayPal for non-EU cardholders.
• Asynchronous Settlement Handling: Payment methods like SEPA Bank Transfer and Sofort take between a few hours to several business days to settle. The add-on assigns the entry an initial status of Pending Payment and seamlessly updates to Paid once Mollie’s background webhook confirms clearance.
• Delayed Admin & Client Notifications: Configure notification routing so that order confirmation emails and digital download links are held until Mollie confirms payment authorization.

5. Troubleshooting & Error Code Matrix

Refer to this matrix when diagnosing Mollie API communication or checkout status errors:

6. Developer Extensibility & Filter Hooks

Custom code can tailor the Mollie payment payload, force specific payment methods programmatically, or pass custom metadata for ERP synchronization.

Customizing Mollie Payment Parameters

Use the filter below to pass order notes, custom customer identifiers, or force specific language locales on the hosted Mollie checkout screen:

/**
 * Customize Mollie transaction payload before creating the payment
 *
 * @param array $payment_data Mollie API payload
 * @param array $feed Current payment feed settings
 * @param array $entry Current Gravity Forms entry
 * @param array $form Current form object
 * @return array
 */
add_filter( 'ge_mollie_payment_payload', function( $payment_data, $feed, $entry, $form ) {
    // Append custom description
    $payment_data['description'] = sprintf( 'Order #%s - %s', $entry['id'], $form['title'] );

    // Pass custom metadata for accounting reconciliation
    $payment_data['metadata'] = [
        'entry_id'         => $entry['id'],
        'form_id'          => $form['id'],
        'affiliate_source' => rgar( $entry, 'source_url' ),
    ];

    // Force German language checkout screen if customer selected Germany
    if ( rgar( $entry, 'billing_country' ) === 'DE' ) {
        $payment_data['locale'] = 'de_DE';
    }

    return $payment_data;
}, 10, 4 );

7. Frequently Asked Questions (FAQ)

Q: Does the customer have to leave my website to pay?

Mollie uses a hosted, conversion-optimized checkout screen that complies with European bank redirect standards (necessary for iDEAL, Bancontact, and 3D Secure). Once authorized, the customer is immediately redirected back to your Gravity Forms confirmation page.

Q: Can I accept recurring subscriptions through Mollie?

Yes. By utilizing Mollie’s Customers API and Mandates (for SEPA Direct Debit or recurring credit card billing), recurring membership and subscription feeds can be provisioned seamlessly.

Q: How do I test the integration safely?

Enter your Mollie Test API Key (starts with test_...) in settings. On the checkout screen, Mollie displays a simulated bank screen allowing you to click Paid, Cancelled, or Expired without spending real funds.