At the moment people give away the purchase history for next to nothing with loyalty cards and such.
Worse still, your so called Doctor knows more about your history than youself. The rightful way you may grand him/her access to your history for some time. Your data, your work, your comment... is your income, your money.
For something to be lawful it has to work both ways. If someone ask of proof of anything, ask for proof first, if satisfied may proceed to next level.
Can Banks & Governments 'Prove Their Wealth'?