This study explores the role of fairness perceptions in driving dishonesty in workplace-like environments. Using a real-effort ball-catching task with systematic variation in task difficulty and opportunity, the study creates both objective unfairness and subjective unfairness, where participants are disadvantaged in one dimension but advantaged in another. The findings show that unfairness substantially increases misreporting, as individuals use perceived disadvantage to justify lying even when the unfairness is subjective and compensated in another dimension. Participants systematically exaggerate their perceived disadvantage, consistent with motivated reasoning that lowers the psychological cost of dishonesty. We also find that highlighting the counting requirement narrows moral wiggle room and significantly curbs cheating in low-opportunity tasks, showing that reducing room for self-serving belief distortion can limit dishonesty. When participants later self-select tasks, dishonest behavior falls sharply as the justification of unfairness disappears, reinforcing the role of perceived disadvantage as a license to lie.