To properly determine the relative tax burdens of different Michigan industries, some measure of the tax base corresponding to Michigan operations must be selected. [21] The appropriate measure would include all of the tax base included in the consumption-based Value-added concept of the SBT, but ignore special adjustments, exemptions, and exclusions. Thus, the tax liability divided by the proper tax base would give an appropriate measure of the relative SBT burden.

As discussed above, the appropriate tax base for a consumption-based VAT like the SBT is gross business income, plus depreciation, plus labor and interest, less capital expenditures: the Adjusted Tax Base. [22] Dividing the tax liability of an industry by its Adjusted Tax Base yields an appropriate tax burden ratio.

The 1985 Treasury Report supports the use of this tax base in their description of the SBT, specifically addressing the expensing of capital expenditures:

Although the SBT base is computed by adding together a number of business costs and some income, the base is equal to sales minus materials and capital purchases. All receipts not used to purchase (or lease) capital and materials represent value-added and are taxed. [23]

Furthermore,

The SBT base is all of the increased value to materials caused by the production process. Although capital expenditures are deducted when made, the value-added because of that capital equipment is reflected in the base and is taxed. Profit, which is the return to the investor, is also part of value-added and is taxed. [24]

And again,

The SBT takes the last approach [a full deduction for capital expenditures]. When a value-added tax allows a full deduction for capital expenditures, it is called a consumption type value-added tax, because, in a national sense, the tax base equals consumption. That is, the base is equivalent to total income less purchases of capital goods, which is total consumption. [25]

However, despite the design of the SBT, which clearly outlines the tax base, and the above reasoning quoted from their report, the Treasury did not choose to use this tax base in their 1985 report.

The tax base the Treasury used, called "Michigan Tax Base," includes all the true tax base without the expensing of capital expenditures.This Michigan Tax Base is computed by adding labor and interest costs to profit, and adding depreciation (all steps taken to reach the true tax base), but not subtracting capital expenditures.

This approach ignores capital expenditures, which distorts significantly the tax base. The measure arrived at bears no conceptual identity with a consumption-type value-added tax, does not represent the SBT base, and does not even resemble a traditional profits tax base. [26]

To give one example of the perverse indications such a tax base would produce, consider that a firm that made a large capital expenditure – such as purchasing a building – would experience no change in its Michigan Tax Base, even though its SBT tax base (the Adjusted Tax Base), its SBT liability, its federal corporate income tax base, and its federal corporate income tax liability would all decline.

The conceptual problem with the Treasury's approach is clear. The SBT, as a VAT, takes into account every employee's wages, all material costs, the interest on bank deposits, and every sale. To exclude capital expenditures from the system would be to turn an extremely broad, inclusive tax into a distorted half-view of a company, where the purchase of a box of paperclips matters more than that of a million-dollar building. [27]

Indeed, the Treasury report flatly states that the correct base to use is the Adjusted Tax Base:

Michigan Tax Base less net capital acquisition deductions, which we call "adjusted tax base," represents the appropriate base of a consumption-type value-added tax. [28]

In addition to the clear evidence to the contrary in the 1985 report, the Treasury's tax base selection contradicted an earlier State government analysis of the SBT. The 1981 Department of Management and Budget (DMB) publication Analysis of the Michigan Single Business Tax: A Business Development Perspective contained similar descriptions of the construction of the SBT as the Treasury's 1985 report and correctly used the Adjusted Tax Base to measure tax burdens across industries. [29] Unfortunately, the 1981 study provided only summaries of the tax burden as a percentage of industry tax bases. [30]

The 1985 Treasury report gave no explanation for its substitution of the Michigan Tax Base for the Adjusted Tax Base, despite its use in the previous analysis and the justification for it in the text of the study.

Since the appropriate measure of the SBT base is the SBT base, the tax burden analyses in this study rely on the Adjusted Tax Base for the Michigan SBT.