An extraordinary item was a gain or loss that was both unusual in nature and infrequent in occurrence, such as certain losses from natural disasters or expropriation. The FASB eliminated the concept with ASU 2015-01, effective for fiscal years beginning after December 15, 2015. Events that would once have qualified are now reported within continuing operations, often as a separate line or disclosed in the notes when material. The XBRL element used for them, ExtraordinaryItemNetOfTax, has been deprecated.
The cumulative effect of an accounting change was the catch-up adjustment a company booked in income when it switched accounting methods, reflecting what earlier periods would have looked like under the new method. SFAS 154, now ASC 250, largely replaced this with retrospective application: prior periods are restated as if the new principle had always applied, and any effect on periods before those presented goes to opening retained earnings rather than through the income statement. When a new standard is adopted, its own transition rules usually direct any cumulative adjustment to retained earnings as well.
For long historical series, this field explains why net income can differ sharply from income before extraordinary items in a given older year. Analysts studying multi-decade earnings trends usually work with income before these items so that one-time accounting catch-ups and rare events do not distort growth rates. Regulation S-X Rule 5-03 now marks the captions that once held these items as reserved.