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This study explores the hypothetical elimination of Japan’s retirement earnings test (ET) for public pensions, focusing on its implications for older workers’ labor supply and pension-claiming behaviors. The ET currently reduces public pension benefits for individuals aged 65 and older if their earnings exceed specified thresholds, potentially discouraging employment in this demographic. Notably, the Japanese ET influences both immediate and future pension benefits, thus diminishing current payouts for working pensioners and foregoing beneficial actuarial adjustments—adjustments based on actuarial calculations that would otherwise increase future benefits to account for delayed pension claims. This dual impact may discourage the labor supply and influence pension-claiming behavior among older workers. Through a survey-based experiment with male workers aged 40–59 years expected to face the ET upon retirement, we assess three reform scenarios as the first study in the literature: (1) eliminating future benefit reductions through actuarial adjustments, thereby enhancing the value of deferred pension claims; (2) removing immediate benefit suspensions to increase current pension payments directly; and (3) a comprehensive reform combining both approaches. Our findings reveal that eliminating reductions through actuarial adjustments increases the intensive margin (labor hours and income) and encourages delayed pension claims. Conversely, removing immediate benefit suspensions influences both the extensive margin (decision to work) and the intensive margin but leads to earlier pension claims. By highlighting the importance of differentiating between immediate and future benefit components in designing ET reforms, this study demonstrates their significant impact on labor supply and pension-claiming decisions.