**UK September 2026 CPI inflation is expected to accelerate from August’s 3.1% print, with the 3.4–3.6% range holding a 59.5% market-implied probability ahead of the October 21 ONS release.** Rising energy and motor fuel costs, driven by Middle East supply concerns, provided the largest upward contribution to the August increase and are anticipated to extend that momentum. The Bank of England’s latest near-term projections already embed further CPI uplift toward 3.7% by year-end, reflecting these external pressures alongside resilient services inflation. Grocery price trends have also ticked higher recently, adding modest breadth to the outlook. While core measures remain contained near 2.6%, traders are pricing limited downside risk below 3.4% given the data trajectory and limited offsetting seasonal factors in the September window.