Which GAAP principle states that all expenses incurred while earning revenue should be reported in the same year as the income is reported?

The GAAP principle that states all expenses incurred while earning revenue should be reported in the same year as the income is recognized is known as the "Matching Principle." This principle ensures that expenses are matched with the revenues they help to generate, providing a more accurate picture of a company's financial performance within a given accounting period. By adhering to this principle, financial statements reflect the true profitability of the business.