What happens if an e-commerce brand ignores sales tax nexus until it becomes a problem?

If an ecommerce brand ignores sales tax nexus until it becomes a problem, they risk back taxes owed to each state for all years they had nexus, plus interest and penalties (which can be substantial). States are increasingly aggressive in pursuing remote sellers post-Wayfair. Voluntary Disclosure Agreements (VDAs) exist to limit lookback periods for brands that come forward proactively before being audited.