<p>The study examines how irregular migration at the Serbian-Romanian frontier affects border mission expenditures, employing an Autoregressive Distributed Lag (ARDL) model over the period from January 2018 to June 2025. This border is under the Territorial Inspectorate of the Border Police in Timișoara (TIBPT) jurisdiction, fully covering the Romanian counties of Timiș, Caraș-Severin, and Mehedinți. The findings indicate that border mission expenditures are influenced by long-term structural factors: smuggling tends to increase these expenditures, while delegation expenditures tend to reduce them. The border mission expenditures also adjust to short-term fluctuations, which are gradually corrected over subsequent months. Immediate adjustments are mainly driven by recent smuggling activity, while other factors have limited short-term influence. Additionally, external shocks, including the pandemic and policy changes, can temporarily constrain border mission expenditures and shift operational priorities. Notably, rising economic policy uncertainty leads to more cautious border mission expenditures, resulting in delayed, reduced, or conservative spending as authorities prioritize financial stability. Not least, the border mission expenditures respond to inflation through higher nominal allocations, compensating for the erosion of their real value.</p>