I am afraid the GoSimpleTax does not support the submission of returns (CT600) for limited companies or submission to companies house. Due to the more complex nature of running a limited company then this process is normally undertaken by an accountant. However, if you wish to file returns for a limited company you can find a list of compatible software on the HMRC website at https://www.gov.uk/government/publications/corporation-tax-commercial-software-suppliers/corporation-tax-commercial-software-suppliers