This study investigates the ex-ante implications of implementing an instant payment system (IPS) in Trinidad and Tobago using a monetarist framework. The paper assumes that an IPS primarily affects the money system with the IPS application being directly linked to individuals’ banking accounts. Therefore, drawing from the quantity theory of money, a Vector Error Correction Model (VECM) is used to assess the impact of an IPS on the velocity of money, inflation expectations and the growth of broad money. The findings, using impulse response functions, reveal that implementing an IPS created sustained increases in money velocity and accelerations in broad money growth, indicating enhanced transactional efficiency. The inflation expectations response exhibits a U-shaped pattern, with initial deflationary pressures followed by eventual inflationary effects. Managing liquidity demand pressures and inflation is recommended via routine surveillance and tailoring stress testing scenarios to include an IPS environment.