Information

See also: copyright
Can I sell my client’s data? A legal distinction worth bearing in mind between between:

• "copyright" - is a statutory right which applies to certain types of information automatically, but does not apply to other kinds of information. Numerical data (like execution prices) is not capable of protection by copyright.
• "information" which can be any kind of information, including data. Parties can make any agreement about who can do what with any type of information, whether or not it is copyrightable. So for example, a client could say "I will only give you my business if you agree not to use any information you derive from by trade data for any purpose other than reporting to me and complying with applicable law." This is a contractual right, not a statutory one, but the client can only enforce it to the extent it can prove that it has suffered a loss. Generally that would be pretty hard to do.
• regulatory/legal considerations: You cannot give non-public information to a third party if that would amount to inside information, or facilitate market abuse (e.g., front running). So if the information identifies a client somehow, especially if it allows prediction of client trading behaviour, you may have a big problem.
• reputational/franchise: Even if there are no legal, contractual, regulatory or criminal sanctions against it, if the client would be annoyed about it and withdraw their business, it's just as big a problem.