Unless mayor White is not telling the truth (which is a distinct possibility---see Can You Trust “$100 Bill” White?), the possible sources of the $90 million seem to be the following:

1. Windfall property tax revenues resulting from Tax Incentive Reinvestment Zones (TIRZs) being brought fully back into the City’s property taxing system. The mayor has given strong indications that he wishes to do so, and Prop G provides that such revenues would be exempt from any city charter caps. It seems totally unfair to not instead use that source of additional revenues to lessen the property tax burden of those taxpayers who have carried the load while the TIRZ businesses were building up their own fiefdoms.
2. Property tax revenues generated by increasing the maintenance and operating portion of the combined tax rate, and temporarily covering the resulting decrease in the debt service portion of the combined tax rate by rolling (refinancing) the City’s long-term debt. You see, the mayor, by just his fiat, holds that his Prop 1 automatically removed the $0.50/$100 cap on the maintenance and operations portion of the property tax rate that was voted into the city charter by Houstonians in the 1980s, even though this devious intended result was never disclosed to the 2004 voters.
3. Property tax revenues that exceed the total property tax revenues cap under the mayor’s Prop 1 passed in 2004. The mayor already has shown that he doesn’t honor even his own law, Prop 1, in that he absolutely refuses to refund to taxpayers the $8 million by which the City’s total property tax revenues exceeded his Prop 1 cap in fiscal 2006.
4. New or expanded other types of fees or charges. You see, other fees and charges are not covered by the mayor’s Prop 1 (which he doesn’t honor anyway) and he proceeds upon the basis that the Prop 2 TABOR is not law.