To the best of your knowledge/belief
Definition 1 of 1
Pro Tip 1/3Legal Statements
Often used in legal contexts to declare information without knowingly lying. 
To the best of my knowledge, the information provided is accurate.
Pro Tip 2/3Honest Uncertainty
Indicates you are truthful, but you accept that there could be things you're unaware of. 
To the best of my belief, all guests have arrived.
Pro Tip 3/3Avoiding Deception
The phrase helps you avoid misleading others if you are unsure about information. 
To the best of my knowledge, the meeting is at 2 PM.