Marketing expenditures represent a significant and growing cost category for firms operating in digital and knowledge-intensive industries. This study examines the accounting, regulatory, and valuation implications of capitalizing marketing spend—including advertising, branding campaigns, and customer acquisition costs—versus treating such expenditures as operating expenses (OpEx) under U.S. GAAP (ASC 350/720) and IFRS (IAS 38). Employing a mixed-methods approach combining doctrinal standards analysis, illustrative adjustments applied to secondary data from 25 publicly listed firms, and multiscenario simulation modeling over a ten-year horizon, this article finds that systematic capitalization of 30–60% of annual marketing spend inflates reported assets by 15–40%, improves short-term EBITDA margins by 12–25 percentage points, and elevates firm valuation multiples by 8–25% in high-growth scenarios. Adjusted NPV estimates under capitalized treatment exceed baseline OpEx NPVs by up to $53M per $500M marketing program, while IRR improvements of 2–5% materially alter capital budgeting acceptance thresholds. However, these benefits are offset by heightened earnings volatility in subsequent amortization periods, elevated risk of regulatory scrutiny from the SEC and PCAOB, and potential valuation reversals upon asset impairment. The study contributes a structured decision framework for CFOs, auditors, and investors to assess whether capitalization produces economically faithful or misleading financial representations.