See Section 3: Accuracy of the Editorial Guidelines.
The BBC's commitment to accuracy is a core editorial value and fundamental to our reputation. Our output must be well sourced, based on sound evidence, thoroughly tested and presented in clear, precise language. We should be honest and open about what we don't know and avoid unfounded speculation.
For the BBC, accuracy is more important than speed and it is often more than a question of getting the facts right. All the relevant facts and information should be weighed to get at the truth. If an issue is controversial, relevant opinions as well as facts may need to be considered.