Gst claim relating to previous year

Nimitha Kundanam (Senior Executive Accountant)   (250 Points)

25 September 2019  
Dear sir

we all know that last date to claim gst inputs is oct 20th. If expenses are not booked relating to previous year...how can we claim gst. should we should expenses of last year in current year as prior period exp and claim exp. kindly explain.