This document provides an overview of open science policies and requirements in Horizon 2020, the EU's research and innovation program. It discusses open access to publications and research data. For publications, beneficiaries must provide open access either immediately (gold) or after an embargo period (green) by depositing the publication in an institutional or subject repository. They can choose between open access publishing or self-archiving. Article processing charges for open access publishing are eligible costs. The document reviews support available through OpenAIRE, including tools to link publications and data to projects and monitor open access compliance.