Hi Michael, I agree with Margarita.
It all depends on the lease that you signed with your landlord. There should be paragraphs that address how the operating expenses are handled to include the real estate taxes, supplemental real estate taxes (if any), real estate insurance, utilities, etc...
It is handled differently depending on the state, type of office space, type of landlord, etc. At the end of the day, it is what was negotiated and agreed to.
A careful review of your executed lease should let you know how such expenses are handled, if you are still unclear and/or it is not addressed explicitly in your lease you may want to consult with a real estate attorney.
May 5, 2015