Unfortunately GoSimpleTax does not support the submission of Trust Tax returns (SA900). We only support the completion of the form SA107 required when an individual receives income from a Trust.
We would recommend you visit the HMRC website at https://www.gov.uk/government/publications/self-assessment-commercial-software-suppliers/self-assessment-online-commercial-software-suppliers and look for a software that details they are SA900 compatiable:
@GoSimpleTax: How do I submit a Trust Return (SA900)?
GoSimpleTax does not support Trust Returns (SA900), so unfortunately you will need to find alternative software
Written by CoCo