A 'Social Enterprise' is a business purpose, not a business form. The tax treatment of a social enterprise will depend on the form of its incorporation. A social enterprise could be a sole trader, a company or a charity (recognised as such by HMRC). Depending on its form, the social enterprise will be taxed in the manner relating to those specific structures, so choose the relevant one from the tax responsibilities block descriptions.
In certain circumstances, specific tax reliefs are available to investors in social enterprises. For more information, please see here.