What term describes the income that is not captured in official statistics due to underreporting?

The term that best describes the income not captured in official statistics due to underreporting is the underground economy. This refers to economic activities that occur outside the formal economy and are not reported to government authorities, often to evade taxation or regulation.

The underground economy includes various transactions and employment arrangements that are conducted informally, where individuals might be paid in cash and not document their earnings. This aspect significantly contributes to a gap in official economic data, as these activities are not accounted for in GDP calculations or economic reports.

By using this term, the concept focuses on the broader range of unreported income, which can include everything from cash jobs to illegal activities, relying on voluntary compliance and honesty of individuals for accurate reporting.