TOPI includes sales and excise taxes, customs duties, property taxes, motor vehicle licenses, severance taxes, other taxes, and special assessments.
Subsidies are counted as a negative value towards TOPI, meaning that they are paying out of TOPI instead of generating TOPI. Because TOPI is net of subsidies, it can be negative for a given Industry in a given year if that Industry received more subsidies from the government than it paid out in these specific taxes in that year. I-O models by default treat TOPI as a leakage, meaning that any TOPI generated as part of an analysis will not generate any additional effects.
Note: TOPI does not include all taxes paid by an Industry. For example, social insurance taxes are a part of Employee Compensation, and profits taxes are part of Other Property Income. Learn more at Understanding TOPI.