Prices excluding fresh food slid 2.3 percent from a year earlier after dropping an unprecedented 2.4 percent in August, the statistics bureau said in Tokyo.
Companies are cutting prices to attract customers whose wages are tumbling.
Retailers are cutting prices more aggressively to attract consumers whose wages have slid for 15 months.
Much of the drop in consumer prices reflects last year’s peak in oil costs. Crude has dropped more than 40 percent since it reached an unprecedented $147.27 a barrel last July.