(payments made by taxpayer to veterinary corporation in course of taxpayer’s trade or business must be reported to IRS in accordance with I.R.C. §6041 if in amount of $600 or more annually; under Treas. Reg. §1.6041-3(p)(1), corporations engaged in providing medical and healthcare services are not exempt from reporting requirement; corporation providing veterinary services is “engaged in providing medical and healthcare services” and is not exempt from information reporting requirement of I.R.C. §6041 as corporate payee).