Fuels constitute one of the most strategically significant categories of goods in the global economy. In many countries, including Poland, fuel prices are determined not only by global market dynamics but also by domestic fiscal instruments such as excise taxes, value-added tax (VAT), and fuel surcharges. The primary objective of this study is therefore to assess the extent to which tax burdens and profit margins shape diesel prices in Poland, thereby providing a deeper understanding of the market’s sensitivity to fiscal interventions and the pricing strategies adopted by fuel companies. The analysis draws on weekly data for the period 2006–2025, encompassing crude oil prices, wholesale and retail diesel prices, and relevant tax components (VAT, excise tax, and fuel surcharges). Methodologically, the study employs the Bai–Perron breakpoint test alongside correlation and comparative methods. The findings indicate that changes in indirect taxation and the fuel surcharge in Poland were predominantly upward and incremental, exerting only limited immediate effects on wholesale and retail fuel prices. This pattern was particularly evident outside of periods of acute geopolitical shocks, such as the 2022 war in Ukraine, when government interventions aimed to mitigate sudden price surges. Moreover, analysis of PKN Orlen’s margin dynamics shows that the company remained consistently profitable, with the highest processing margins observed following the reduction of the VAT rate, highlighting the interplay between fiscal policy and corporate pricing behavior. An exception occurred in 2022, when political involvement led to negative retail margins despite a reduction in VAT, a policy decision intended to mitigate sharp increases in fuel prices. The evidence suggests that petrochemical companies have greater capacity to affect prices through adjustments to wholesale margins than to retail margins. The study also underscores the critical role of fiscal policy in protecting households from fuel price volatility. It also demonstrates that carefully designed adjustments to taxation and other fiscal instruments can meaningfully influence market outcomes and corporate profitability, thereby highlighting their importance in broader economic stabilization efforts.