The reason you have been notified to file Corporation Tax is likely because you have not informed HMRC of your company's dormant status.

Please note that Companies House does not share information with HMRC regarding companies that have submitted dormant accounts.

You must contact HMRC’s Corporation Tax office in writing to inform them that your company is dormant. You should also state the date from which the company became dormant.

You can find these contact details on any official letter that HMRC has sent to your registered office address. Alternatively, you can find Corporation Tax office details online.