Thank you for the additional information. What you are asking about is a pre-authorization hold. You would need to contact your credit card processor to find out what their operating guidelines are for such holds. Typically, they are used for when the amount of the service is unknown. In your case, you do know what services they are being charged for. Your problem is with not knowing how much their insurance will cover, if they have insurance. In such a case, the credit card merchant will most likely not allow such a hold. You would have to do what every other provider does and that is to bill the patient/client for any amount not covered by insurance and send it to collections if the bill is not paid. It's part of the cost of doing business
. Ultimately, however, it is the credit card processor and Visa and Mastercard that determine whether or not to allow holds. Also, the holds are only allowed for a certain time. In the case of a hotel, for example, you have a set period of time, i.e. when the guest leaves. In the case of a medical provider, they are in and out and so there would be no basis for putting a hold for days. That is why my guess is that the credit card bank would not allow this.
Also, keep in mind that consumer laws require that you notify customers/clients about any fees and so, if you were to do this, you would need to notify them upfront. This might detract people from using your clinic if they have insurance with only a 20 dollar deductible, for example, and then they come in and you tell them they are going to take out 100 from their account no matter what, until you can verify things with their insurance company.