It is a good practice requirement that all the results are made publicly available within 12 months of study completion (last participant, last visit). This applies no matter whether the results are positive, negative, neutral or inconclusive. The UK Policy Framework for Health and Social Care Research says:
Other than research for educational purposes and early phase trials, the findings, whether positive or negative, [should be] made accessible, with adequate consent and privacy safeguards, in a timely manner after they have finished.
Summary results including key outcomes should be posted to the results section of the register(s) where the research project is registered.
If the register used does not have a results section, the results should be posted on a free-to-access, publicly available, searchable institutional website of the sponsor, funder or chief investigator.
Where the main findings are also to be submitted for publication in a journal, this should be done within 12 months of study completion, to be published through an open-access mechanism in a peer-reviewed journal.