You must receive a Certificate of Assumed Name from your county clerk. This certificate is often called a "business certificate."To file as a single proprietor, the Blumberg form is X201. To file as a partnership, the Blumberg form is X74. You must file the certificate in the office of the County Clerk in the county where your business is located. Get the Certificate of Assumed Name form. Welcome to our home for businesses. We designed it to provide easy access to tax information, filing and payment resources, and popular business topics. Create a Business Online Services account to file and pay New York State business taxes, including corporations tax, sales tax, withholding tax, and more. Tax Forms for Business Licenses, Property Taxes, Real Estate Tax, and Prior Year Forms.