Every association or society organized and operating under this article solely as a nonprofit medical indemnity or hospital service association or society or both shall be, from the time of such organization, exempt from every state, county and municipal tax, except unemployment compensation tax. Nothing in this section shall be deemed to exempt the association or society from liability to withhold the taxes payable by its employees and to pay the same to the proper collection officers, and to keep such records, and make such returns and reports, as may be required in the case of other corporations, associations or societies similarly exempted from such taxes.