Guidance

Important information for software developers - read first

Updated 17 March 2025

You must read this guidance before reading the technical interface specification (TIS).

We plan to replace our XML platform with our (REST JSON) API in the long-term future. We do not have a definite timetable for this yet, but you should consider this before developing an XML gateway-based service.

Applying for a test account

Before you start, you鈥檒l need to read and understand the contents of our specification. If you decide to start development, you鈥檒l need to set up your test account first.

To activate a test account, you鈥檒l need to give us the presenter鈥檚:

  • name
  • contact name
  • address
  • email address
  • telephone number

To apply for your test account, send us these details by email: [email protected]

Apart from the address, these are usually the developer鈥檚 details. Our main contact during testing is usually the development team, and not the presenter or company.

We鈥檒l use these details to activate a test account. We鈥檒l then give you the test presenter credentials which you must use in all test submissions.

To make sure test cases are effective, your test data should closely resemble 鈥榬eal life鈥� data.

Testing guidance

Your test submissions will be examined or 鈥榩arsed鈥� by the gateway. Submissions will be automatically rejected if it detects any errors.

Your test account will only store submissions which have successfully parsed the gateway. These submissions need to be manually reviewed by Companies House and will stay pending until we鈥檝e reviewed them.

You鈥檒l need to tell us when you鈥檝e made test submissions, so we can review them. Contact us by email: [email protected]

The will need to be tested with the test flag set to 1. See 鈥楳ore info鈥� for available examples.

You鈥檒l need to use a unique submission (envelope) number for each of your submissions, so we can check and respond to your test submissions.

Read the technical specifications for guidance on submissions and responses. The diagram explains what communications to expect between you and Companies House.

These documents cover technical guidance only, and not the legal requirements of running a business.

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Submitting attachments within XML

All incorporation submissions must have at least one attachment within the XML <Document> element. This also applies to some other document types.

You should test all variations of the image attachments.

If a company is using modified or bespoke articles of association, you鈥檒l need to test these attachments. You do not need an attachment if the company is using 鈥榤odel鈥� articles of association.

You should also test any attachment letters that give permission or justification to use a company name that:

  • includes a 鈥榮ensitive鈥� word or expression
  • is considered the 鈥榮ame as鈥� another company name registered

Creating attachment images

  1. Save the document in one of the specified and supported PCL or PDF formats.
  2. Compress this into a base64 string.
  3. Paste the created base64 string into the XML <Data> element.

This information applies to the 鈥榠nput鈥� (filing) version of the XML gateway only.

To develop a 鈥榥ame availability search鈥� for your incorporation software, you鈥檒l need the 鈥榦utput鈥� (search) version of the XML gateway. Email [email protected] for more information.

Completion of testing

Testing is complete when Companies House is confident that the development, relevant to the form types being tested, meets our strict criteria.

You鈥檒l then need to apply for an online filing presenter account, if you do not have one already, and we鈥檒l send you a presenter ID.

.

- see 鈥楳ore info鈥� for available examples.

Troubleshooting: common testing issues

No response to test submission whatsoever

You鈥檒l need to confirm the URL you鈥檝e used, and email your XML test submission to [email protected]

No further response to test submission after initial acknowledgement

All status requests must be polled for. Visit for the relevant 鈥楪et submission status鈥�, 鈥楪et status ack鈥� and 鈥楪et document鈥� schemas.

Pending response received

This applies to test submissions that include an attachment. Email [email protected] to let us know and we鈥檒l review your test, and change the status accordingly.

Reject reason: 502 Error

Check that both your sender (test presenter ID) and authentication value is correct and properly MD5# coded.

Check that the test flag is set to 1.

Check that the value is shown as 鈥榗lear鈥�.

Check that the package reference is 0012.

Reject reason: Failure - multiple tests

You have submitted multiple tests with the same submission number.

So we can check and respond to your test submissions, you鈥檒l need to use a unique submission (envelope) number for each of your submissions. For guidance on submissions and responses, the technical specification contains a diagram of the communications you can expect between you and Companies House.

Reject reason: Only non-electronic filing accounts can access this service

You鈥檝e probably tried to submit a 鈥榮earch request鈥� for a company name, data or images.

These options are not available through our software filing gateway. For information on our searchable software options, visit: