---
title: "Prepopulate a Merchant Signup Form"
slug: "prepopulate-a-merchant-signup-form"
updated: 2026-07-17T21:08:25Z
published: 2026-07-17T21:08:25Z
canonical: "resource.payrix.com/prepopulate-a-merchant-signup-form"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://resource.payrix.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Prepopulate a Merchant Signup Form

You can prepopulate parts of the Merchant Signup Form with data from your platform or customer relationship management (CRM) system. Prepopulated forms reduce manual entry, reduce errors, and speed up onboarding to help you guide merchants through a more focused signup experience.

## Overview

The Merchant Signup Form is a branded and Payrix Pro-hosted form created during your sandbox onboarding. The Payrix Pro Implementations team provides your signup URL:

```http
https://test-portal.{yourBrand}.com/signup/{yourCode}
```

- `{yourBrand}`: Your branded domain.
- `{yourCode}`: The unique path for your form, found on the [Signup Forms](/v1/docs/signup-forms) page in the Payrix Pro portal.

The form submits data to the Payrix Pro API. This means prepopulated values must follow the formats and field rules defined in the API specification. See the [Supported Query Parameters](/v1/docs/prepopulate-a-merchant-signup-form#merchant-signup-form-query-parameters) section for more details.

## Prepopulate Fields with URL Query Parameters

You can add query parameters to your Merchant Signup Form link to prepopulate nonsensitive fields. When merchants open the link, the form loads these values first so that merchants can focus on required fields that need direct input.

### Requirements

All prepopulated values must follow these rules:

- Queries must not contain SSNs, EINs, TINs, third-party IDs, bank account details, or other PCI-regulated data.
- Queries must not contain merchant attestations, agreements, or other consent fields.
- Values containing special characters must be [URL encoded](/v1/docs/prepopulate-a-merchant-signup-form#special-character-encoding).

> [!WARNING]
> Important!
> 
> Sensitive data must be entered by the merchant inside the secure form. Public URLs are not encrypted.

### Bracket Notation Syntax

Some Payrix Pro API fields use nested data. The Merchant Signup Form maps these fields using bracket notation. This format shows each value's place inside the nested payload. Each bracket represents one level in the `POST /entities` [API request](https://docs.worldpay.com/api-specification/payrix/partner#/rest/welcome-to-payrix-pro/api-endpoints/entities/post-entities) data.

Nested objects appear in brackets when they are nested within another object. For example, the `members` object nests within the `merchant` object:

```http
merchant[members]
```

When an object contains an array of resource payloads, the list items use numeric indexes starting at `[0]`. The index shows which record you are targeting.

For example, to set the `first` field for the first and second members inside the `merchant.members` array, use:

```http
?merchant[members][0][first]=Robert&?merchant[members][1][first]=Steven
```

This tells the form to place the value inside the `merchant` object, then inside the `members` list, then inside each `member`, and finally into both members' `first` field.

### Special Character Encoding

You must [URL encode](https://www.w3schools.com/tags/ref_urlencode.ASP) special characters before adding values to the query. This includes characters like spaces (non-breaking spaces), apostrophes, at signs, and ampersands.

For example, to encode the special characters in *Bob's Bike Store*:

- Encode each space as `%20`.
- Encode the apostrophe as `%27`.

The final encoded string is:

```http
Bob%27s%20Bike%20Store
```

## Supported Query Parameters

You can prepopulate most fields defined in the API requests that power the form:

- `POST /entities`
- `POST /merchants`
- `POST /members`

See the [Payrix Pro API specification](https://docs.worldpay.com/api-specification/payrix/partner) in the Worldpay Developer Hub for details about the relevant fields, including each field’s format and valid values.

## Common Prepopulation Scenarios

See the following examples for real-world applications of prepopulated forms.

### Industry Default Codes

If your platform supports only one industry, you can prepopulate the MCC and NAICS codes with the related description:

```http
https://test-portal.example.com/signup/sandbox?merchant[mcc]=5940&merchant[naics]=459110&merchant[naicsDescription]=Sporting%20Good%20Retailers
```

### Known Merchant Member Contact

If merchants sign up through your custom application dashboard and you already store their ownership details, you can prepopulate them in the form:

```http
https://test-portal.example.com/signup/sandbox?merchant[members][0][first]=Robert&merchant[members][0][middle]=Karl&merchant[members][0][last]=Wheelwright&merchant[members][0][email]=bob%40bobsbikes.com&merchant[members][0][phone]=5555555555&merchant[members][0][ownership]=10000
```

The process of adding clients (merchants) to the Payrix Pro platform to use the Payrix Pro payment solutions. Also known as *boarding*.

A PayFac-as-a-service platform. Software companies can act as payment facilitators without taking on the associated risks, compliance burdens, and investment.