Knowledge base

What Is a Companies House Authentication Code?

Published 13/06/2025Last updated 08/10/2026

This 6-character code (e.g., ABC12D) is your key to filing updates and returns with Companies House. It’s usually sent by post a few weeks after incorporation.

If you’ve moved to Mighty from another accountant, we’ll reach out to them to get this for you during our professional clearance process so you don’t need to worry about tracking it down, as we'll add this into Mighty for you. 

Can’t find your code? No problem. You can log in or create an account on Companies House WebFiling to request a new one here.

Need help? Just drop us an email at support@mightyaccounting.com, and we’ll sort it out.

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