Some patients will need to ask in order to determine whether or not they are fully covered. Some will need to know to see if they can afford your treatment. In both cases the patient is then able to make an informed choice.
The key here is to minimise surprises.
The BMA (British Medical Association) and FIPO (Federation of Independent Practitioner Organisations) both recommend agreeing fees in advance with the patient wherever possible. This can be easily achieved by publishing them on your website.
You do not need to know all your fees, if you have a point of reference somewhere else. Such as a website, an insurance company fee schedule, or a knowledgeable person. But be careful if you do quote your charges, because the patient will remember what you said and you may be bound by that answer.