PurposeThe present research aims at identifying the latent factors that are driving the rise of the shadow economy in Palestine, assesses its magnitude from 1998 to 2021 and investigates the influence that its size has on the financial sustainability of Palestine's public budget.Design/methodology/approachThe researchers employed the multi-indicator multi-causes (MIMIC) model to estimate the size of the shadow economy and investigate its effect on the financial sustainability of the public budget. Economic factors such as direct taxes, indirect taxes, government welfare, government spending and unemployment were considered causal variables, while indicators of financial sustainability included budget deficit, public debt and gross domestic product (GDP). The shadow economy served as an intermediary variable.FindingsBased on the findings, the researchers recommend regulating and formalizing legitimate activities within the shadow economy. Additionally, they suggest promoting investment projects to reduce unemployment rates, lowering taxes on essential goods and consumer items and providing support to local producers in Palestine. These measures aim at addressing the challenges posed by the shadow economy and fostering economic stability.Originality/valueThe study reveals that the average size of the shadow economy in Palestine between 1998 and 2021 was 43.80%, fluctuating within the range of 39.92%–46.30%. It further establishes that an increase in direct and indirect taxes as well as unemployment contributes to the expansion of the shadow economy. Conversely, government welfare and spending exert a diminishing effect. Moreover, the study finds that the rise of the shadow economy correlates with an increase in public debt, budget deficit and GDP, indicating a negative impact on the financial sustainability of the public budget.