Checkout Page

At a glance

The Checkout Page is a Monek-hosted payment page. You send the customer to it, they pay, and they come back to your site. Card details never touch your servers.

Use the Checkout Page for website checkouts and shopping carts. To keep customers on your own page with embedded card fields, use the Checkout SDK instead. For refunds and repeat charges, use the Payments API.

Try it

Walk through a Checkout Page payment step by step. This is a simulation: nothing is sent to Monek.

Demo only. Nothing is sent to Monek and no payment is taken.

1. 1Prepare
2. 2Redirect
3. 3Pay
4. 4Result

1. Your server prepares the payment

Enter the order details. Your server sends them to Monek to get a payment token.

Amount (£)Payment reference

Try 25.00 (approved), 75.00 (referred) or 120.00 (declined). These follow the same rules as a Monek test account.

The request your server sends:

POST /Secure/iPayPrepare.ashx HTTP/1.1
Host: elite.monek.com
Content-Type: application/x-www-form-urlencoded

MerchantID=0000000&Amount=2500&CountryCode=826&CurrencyCode=826&MessageType=ESALE_KEYED&Dispatch=NOW&ResponseAction=REDIRECT&ThreeDSAction=ACSDIRECT&SuccessUrl=https%3A%2F%2Fwww.example.com%2Fpayments%2Fsuccess&FailureUrl=https%3A%2F%2Fwww.example.com%2Fpayments%2Ffailure&PaymentReference=ORDER-1001&PreparedPaymentAction=JSON

Before you start

Testing your integration

Staging is not a sandbox. To test your integration, request a test Merchant ID from support@monek.com. Test Merchant IDs return simulated responses based on the transaction amount. See Test Cards for the expected responses.

Never send real card details to a test Merchant ID, and never use your live Merchant ID for testing on either gateway.

Gateway URLs

Gateway URLs

Primary:

• https://elite.monek.com/Secure/iPayPrepare.ashx - Checkout Prepare
• https://elite.monek.com/Secure/Checkout.aspx - Full Checkout
• https://elite.monek.com/Secure/CheckoutLite.aspx - Simple Checkout

Staging:

• https://staging.monek.com/Secure/iPayPrepare.ashx - Checkout Prepare
• https://staging.monek.com/Secure/Checkout.aspx - Full Checkout
• https://staging.monek.com/Secure/CheckoutLite.aspx - Simple Checkout

Both gateways are live and will process payments for all Monek merchant accounts. Staging gives early access to new features before they reach the primary platform.

Take a payment

Step 1: Create a payment token

Your server sends the payment details to iPayPrepare.ashx and gets back a Prepared Payment token. Doing this server-to-server keeps your merchant and transaction details out of the customer's browser.

Request encoding

Requests are sent as a standard HTML form submission. Use HTTP POST with a Content-Type of application/x-www-form-urlencoded, with each field name and value URL-encoded in the request body. Query string parameters on an HTTP GET are also accepted, but POST is recommended so that transaction data is not written to browser history or server logs.

JSON and XML request bodies are not supported. The JSON and XML options (ResponseAction and PreparedPaymentAction) only control the format of the response.

The following examples create a Prepared Payment Token for a £10.00 sale and request the token back as JSON:

HTTP

POST /Secure/iPayPrepare.ashx HTTP/1.1
Host: staging.monek.com
Content-Type: application/x-www-form-urlencoded

MerchantID=0000000&Amount=1000&CountryCode=826&CurrencyCode=826&MessageType=ESALE_KEYED&Dispatch=NOW&ResponseAction=REDIRECT&ThreeDSAction=ACSDIRECT&SuccessUrl=https%3A%2F%2Fwww.example.com%2Fpayments%2Fsuccess&FailureUrl=https%3A%2F%2Fwww.example.com%2Fpayments%2Ffailure&PaymentReference=ORDER-0001&PreparedPaymentAction=JSON

cURL

curl -X POST https://staging.monek.com/Secure/iPayPrepare.ashx           -H "Content-Type: application/x-www-form-urlencoded"           --data-urlencode "MerchantID=0000000"           --data-urlencode "Amount=1000"           --data-urlencode "CountryCode=826"           --data-urlencode "CurrencyCode=826"           --data-urlencode "MessageType=ESALE_KEYED"           --data-urlencode "Dispatch=NOW"           --data-urlencode "ResponseAction=REDIRECT"           --data-urlencode "ThreeDSAction=ACSDIRECT"           --data-urlencode "SuccessUrl=https://www.example.com/payments/success"           --data-urlencode "FailureUrl=https://www.example.com/payments/failure"           --data-urlencode "PaymentReference=ORDER-0001"           --data-urlencode "PreparedPaymentAction=JSON"

C#

using System.Net.Http;
using System.Text.Json;

public sealed class MonekPreparedPaymentResponse
{
    public string Token { get; set; } = string.Empty;
    public DateTimeOffset? ExpiryDate { get; set; }
}

public sealed class MonekCheckoutService(HttpClient httpClient)
{
    private const string PrepareUrl = "https://staging.monek.com/Secure/iPayPrepare.ashx";
    private const string CheckoutUrl = "https://staging.monek.com/Secure/Checkout.aspx";

    /// <summary>Creates a Prepared Payment Token and returns the Checkout page URL to redirect the cardholder to.</summary>
    public async Task<string> PreparePaymentAsync(string orderReference, int amountInPence, CancellationToken ct = default)
    {
        var fields = new Dictionary<string, string>
        {
            ["MerchantID"] = "0000000",
            ["Amount"] = amountInPence.ToString(),
            ["CountryCode"] = "826",
            ["CurrencyCode"] = "826",
            ["MessageType"] = "ESALE_KEYED",
            ["Dispatch"] = "NOW",
            ["ResponseAction"] = "REDIRECT",
            ["ThreeDSAction"] = "ACSDIRECT",
            ["SuccessUrl"] = "https://www.example.com/payments/success",
            ["FailureUrl"] = "https://www.example.com/payments/failure",
            ["PaymentReference"] = orderReference,
            ["PurchaseDescription"] = $"Order {orderReference}",
            ["PreparedPaymentAction"] = "JSON",
            ["PreparedPaymentMinutes"] = "30"
        };

        // FormUrlEncodedContent sends Content-Type: application/x-www-form-urlencoded
        using var content = new FormUrlEncodedContent(fields);
        using var response = await httpClient.PostAsync(PrepareUrl, content, ct);
        var body = await response.Content.ReadAsStringAsync(ct);
        response.EnsureSuccessStatusCode();

        // Response: {"Token":"...","ExpiryDate":"2024-01-01T12:00:00+00:00"}
        var prepared = JsonSerializer.Deserialize<MonekPreparedPaymentResponse>(
            body, new JsonSerializerOptions { PropertyNameCaseInsensitive = true });

        if (string.IsNullOrWhiteSpace(prepared?.Token))
            throw new InvalidOperationException($"No Prepared Payment token returned: {body}");

        return $"{CheckoutUrl}?PaymentToken={Uri.EscapeDataString(prepared.Token)}";
    }
}

The fields you'll use most are listed under Key fields.

Step 2: Send the customer to the Checkout Page

Redirect the customer to Checkout.aspx (or CheckoutLite.aspx for a simpler page) with the token in the PaymentToken field. The redirect works with HTTP GET or HTTP POST, and the page can be shown in an iframe.

https://elite.monek.com/Secure/Checkout.aspx?PaymentToken=YOUR_TOKEN

If you show the Checkout Page in an iframe and want Apple Pay, register your domain first.

Step 3: The customer pays

The customer enters their card details on the Checkout Page. With ThreeDSAction=ACSDIRECT, TransactDirect handles 3-D Secure for you:

• If the card issuer approves without a challenge (frictionless flow), the payment goes straight to authorisation.
• If the issuer asks for a challenge, the customer is sent to their bank's authentication page and then straight back.

Step 4: Handle the result

With ResponseAction=REDIRECT, the customer is sent to your SuccessUrl or FailureUrl with the result in the query string:

https://www.example.com/payments/success?ResponseCode=00&Message=AUTHCODE%3A01223&CrossReference=03050711535801223303

• ResponseCode 00 means the payment was authorised. Any other code means it wasn't. See Response Code Values.
• Store the CrossReference. You'll need it for refunds and any later charges.

Confirm orders by webhook

A customer can close their browser before the redirect completes. Set a WebhookUrl so Monek sends the result straight to your server, and use the Integrity Digest to check that results are genuine. See Webhooks.

Key fields

These are the fields most Checkout Page integrations need.

Looking for a field that isn't here?

The full list of every request and response field is in the Field Reference.

Field	Typical value	Notes
MerchantID	Your 7-digit Monek ID	Use your test Merchant ID until you go live.
Amount	1000	In pence, with no decimal point. 1000 = £10.00.
CurrencyCode	826	Pound Sterling. See currency codes.
CountryCode	826	United Kingdom.
MessageType	ESALE_KEYED	An online sale. See message types.
Dispatch	NOW	Use LATER to authorise now and settle later. See Deferred Dispatch.
ResponseAction	REDIRECT	Send the customer back to your site with the result.
ThreeDSAction	ACSDIRECT	Monek handles 3-D Secure for you.
SuccessUrl / FailureUrl	Your result pages	Where the customer goes after paying.
PaymentReference	Your order number	Shown in the Monek Portal and returned with the result.
WebhookUrl	Your webhook endpoint	Recommended. See Webhooks.
CardholderName	Customer's name	Needed for 3-D Secure.
EmailAddress or PhoneNumber	Customer's email or phone	One is required for Visa 3-D Secure.

Customise the page

Add these fields to your payment request to change what the customer sees.

Field Name	Description	Req'd	Size	Type
CancelUrl	Adds a cancel link to the checkout page which will redirect to the supplied URL.	O	V	A
CancelPrompt	Overrides the default cancel link label of "Cancel and return to merchant name" with the supplied prompt.	O	V	A
CssIntegrity	Optionally allows the contents of CSS URL to be verified using the Subresource Integrity mechanism. For further information see: https://www.srihash.org/	O	V	A
CssUrl	References an external stylesheet to enable merchant customisation of hosted payment page. If set, this must be a fully qualified URL.	O	V	A
ShowGooglePay	Indicates if the Google Pay™ button will appear on the checkout page. YES or NO (default) All merchants must adhere to the Google Pay APIs Acceptable Use Policy and accept the terms defined in the Google Pay API Terms of Service. Google Pay is a trademark of Google LLC.	O	3	A
ShowApplePay	Indicates if the Apple Pay button will appear on the checkout page. YES (default) or NO Note: If hosting the Checkout page in an iFrame you will need to register your domain See: Apple Pay.	O	3	A
ShowPayPal	Indicates if the Pay Pal button will appear on the checkout page. YES or NO (default). PayPal requires additional merchant configuration, contact Monek Support for details.	O	3	A
ShowAddressDetails	Indicates whether the address details will be shown on the checkout page. YES (default) or NO	O	3	A
ShowDeliveryAddress	Indicates whether the delivery address will be shown on the checkout page. YES or NO (default)	O	3	A
ShowSaveCard	Shows a "save card details for future use" checkbox on the checkout page. Ticking it is the same as sending AcceptCOF=YES. Options are YES (optional checkbox), MANDATORY (the checkbox must be ticked before the customer can pay) or NO (default).	O	9 max.	A

O = Optional, V = Variable Length, A = Alpha-Numeric

Recommended features

• Prepared Payments provide a secure way to protect merchant and transaction details with a simple redirect token.
• Idempotency Tokens provide a reliable way to protect against against duplicate transactions and replay events.
• The Integrity Digest provides a secure method to verify that responses, redirects, and webhooks are genuine and unmodified.
• Webhooks provide a simple notification service for transaction results without relying on the cardholder transaction flow.
• Basket Details provides an updated and flexible method of sending itemised basket details for your transaction that also satisfies required transaction details for American Express.
• Apple Pay if you want to embed our checkout page in an iframe on your website, you will need to register your domain in order for Apple Pay to function.

Go-live checklist

• Swap your test Merchant ID for your live one.
• Create payments with Prepared Payments so transaction details stay off the customer's browser.
• Set a WebhookUrl and confirm orders from the webhook, not only the redirect.
• Check your SuccessUrl and FailureUrl point at your live site over https.
• Send CardholderName, and EmailAddress or PhoneNumber, so 3-D Secure works smoothly.
• If you use an iframe with Apple Pay, register your domain.