Support
Stuck on a filing, or have a question about how OneFiler works? We're happy to help.
Email us
The fastest way to reach us is by email. We read every message and will get back to you as soon as we can.
support@onefiler.co.ukTo help us help you faster
When you email, it speeds things up if you include:
- Your company registration number (CRN).
- What you were trying to do, and what happened.
- Any error message you saw, or a screenshot.
Please don't email us your Government Gateway password, UTR, or company authentication code — you never need to share those with us, and we'll never ask for them.
Before you email
Many questions are answered in our guides and FAQ:
- Frequently asked questions — eligibility, dormant companies, deadlines, security.
- Guides — step-by-step help for filing your CT600 and accounts.
- Free tools — deadline calculator, micro-entity checker, tax estimator.
What we can and can't help with
We can help you use the software — navigating the filing flow, importing figures, understanding a rejection, or a problem with your account. We are a software tool, not a regulated tax adviser, so we can't give you tax advice or tell you what to put on your return. If you're unsure about your tax position, please speak to a qualified accountant.