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Amicus Brief In Maryland Comptroller V. Wynne, Michael S. Knoll, Ruth Mason

All Faculty Scholarship

The internal consistency test reveals that Maryland applies systematically higher “county” taxes to interstate commerce than to in-state commerce.

Economic analysis of Maryland’s tax regime — including its taxes on inbound, outbound, and domestic activities — confirms what the internal consistency test suggests, namely, that the Maryland “county” tax discourages interstate commerce. Specifically, the Maryland tax regime discourages Maryland residents from earning income outside of Maryland, and it simultaneously discourages nonresidents from earning income in Maryland. Maryland alone causes this distortion; the distortion does not depend on the taxes imposed by any other state.

Petitioner’s argument that Maryland’s outbound tax …