Nexus is the minimum connection that a state needs to have with a taxpayer in order to impose tax; this varies greatly by state and tax type. Determining if a business is required to file tax returns in a particular state requires a comprehensive understanding of the business plus federal and state laws, and relevant court cases.
Most businesses are not filing tax returns in the proper states; some file in too many, some file in too few, and some are filing in the wrong states. Failing to file can lead to substantial tax liabilities and penalties. Filing in too many states is costly as well. My nexus studies determine where the business is required to file. I also provide a risk assessment by state which provides information necessary for you to make a business decision about where to file.