How to disable email editing in checkout

If a buyer is already signed into your app, you usually don’t want them retyping (or fat-fingering) their email at checkout. A typo there means a stranded order, a duplicate customer record, and a reconciliation headache later. The fix: attach the checkout session to a customer you already know. When you do, Macropay treats the email as settled — it pre-fills the field and locks it so it can’t be changed.

What attaching a customer does

Pass customer_id or external_customer_id to checkouts.create and Macropay will:

Pre-fill the customer’s known details into the checkout form.
Lock the email field so the buyer can’t edit it.
Bind the resulting order to that exact customer record — no duplicates, clean reconciliation.

Because Macropay is the Merchant of Record, that locked customer record is also what we use to assess the right sales tax/VAT and to put the correct legal seller on the buyer’s statement. One trustworthy identity in, one clean tax-compliant order out.

Pick the right identifier

Identifier	Use when	Why
`external_customer_id`	You run your own auth / user table	Recommended. Map straight to your internal user ID — reconciliation stays trivial and you never store our UUID.
`customer_id`	The customer already exists in Macropay and you hold our UUID	Direct, unambiguous link to an existing Macropay customer.

Option A — link by your own user ID (recommended)

If you already manage users, hand us your internal ID as external_customer_id. Macropay looks for a customer with that external ID; if one exists it links to it and pre-fills their data, and either way the order ends up attributed to that ID.

Create the checkout with external_customer_id

Pass your application’s user ID. Here a logged-in user upgrades to the pro-annual plan:

import { Macropay } from "@macropayments/sdk";

const macropay = new Macropay({ accessToken: process.env["MACROPAY_ACCESS_TOKEN"] });

const checkout = await macropay.checkouts.create({
    products: ["<product_id>"],
    externalCustomerId: "user_8f3a91", // your app's user ID
});

console.log(checkout.url);

from macropay_sdk import Macropay

with Macropay(
    access_token="<YOUR_BEARER_TOKEN_HERE>",
) as macropay:

    checkout = macropay.checkouts.create(request={
        "products": ["<product_id>"],
        "external_customer_id": "user_8f3a91",  # your app's user ID #
    })

    print(checkout.url)

curl --request POST \
  --url https://api.macropay.ai/v1/checkouts/ \
  --header 'Authorization: Bearer <YOUR_ACCESS_TOKEN>' \
  --header 'Content-Type: application/json' \
  --data '{
    "products": ["<product_id>"],
    "external_customer_id": "user_8f3a91"
  }'

Send the buyer to checkout

Redirect to the url in the response. The email arrives pre-filled and read-only, and the order comes back stamped with user_8f3a91.

Option B — link by Macropay customer ID

If the customer already lives in Macropay and you have our UUID, link to it directly.

Grab the customer ID

Find it in your dashboard’s customer list or via the API. It’s a UUID, for example 992fae2a-2a17-4b7a-8d9e-e287cf90131b.

Create the checkout with customer_id

import { Macropay } from "@macropayments/sdk";

const macropay = new Macropay({ accessToken: process.env["MACROPAY_ACCESS_TOKEN"] });

const checkout = await macropay.checkouts.create({
    products: ["<product_id>"],
    customerId: "992fae2a-2a17-4b7a-8d9e-e287cf90131b", 
});

console.log(checkout.url);

from macropay_sdk import Macropay

with Macropay(
    access_token="<YOUR_BEARER_TOKEN_HERE>",
) as macropay:

    checkout = macropay.checkouts.create(request={
        "products": ["<product_id>"],
        "customer_id": "992fae2a-2a17-4b7a-8d9e-e287cf90131b",  
    })

    print(checkout.url)

curl --request POST \
  --url https://api.macropay.ai/v1/checkouts/ \
  --header 'Authorization: Bearer <YOUR_ACCESS_TOKEN>' \
  --header 'Content-Type: application/json' \
  --data '{
    "products": ["<product_id>"],
    "customer_id": "992fae2a-2a17-4b7a-8d9e-e287cf90131b"
  }'

Send the buyer to checkout

Redirect to the returned url. The email field is pre-filled and locked, and the order links back to that customer.

Building agent or usage-based billing? The same trick keeps your records clean: bind every checkout to an external_customer_id and downstream usage events, meters, and agent value receipts all roll up under one stable customer — so per-customer revenue and margin stay accurate without any post-hoc stitching.

Getting Started

Guides

How to disable email editing in checkout

What attaching a customer does

Pick the right identifier

Option A — link by your own user ID (recommended)

Option B — link by Macropay customer ID

​What attaching a customer does

​Pick the right identifier

​Option A — link by your own user ID (recommended)

​Option B — link by Macropay customer ID

What attaching a customer does

Pick the right identifier

Option A — link by your own user ID (recommended)

Option B — link by Macropay customer ID