Unincorporated businesses subject to tax under a local law of the city imposing a tax on utilities shall not be subject to tax under this part; provided, however, that unincorporated businesses, other than utility businesses subject to the supervision of the state department of public service, which are subject to tax under a local law of the city imposing a tax on vendors of utility services shall be subject to tax under this part on that percentage of their entire net income allocable to the city under section one hundred seven which their receipts other than those taxable under such local law taxing vendors of utility services is of their total receipts. If an individual or an unincorporated entity carries on two or more unincorporated businesses, all such businesses shall be treated as one unincorporated business for the purposes of this title.
N.Y. General City Model Law § 103