January Series F&O Setup: Lot size change, seasonality factor and other key triggers

Today's session, the final day of 2025, will mark the end of the year, but the beginning of a new F&O series.

The January series brings with it a lot of changes. First, the Nifty lot size has been cut down to 65 from 75 earlier. Additionally, the Nifty Bank lot size has also been cut down to 30 from 35.

Four stocks, Swiggy, Bajaj Holdings, Waaree Energies and Premier Energies will begin trading in the Futures & Options segment starting today.

Nifty ended the December series with very little moves, taking the cumulative moves over the last two series down to nearly zero. The index was up 54 points in the December series, compared with the 51 point drop in November.

F&O Series	Returns (Points)
December 2025	54
November 2025	-51
October 2025	1,325
September 2025	110
August 2025	-267

The Nifty grapples with seasonality in the January series. The last four years has seen the Nifty deliver negative returns in every single January series.

January Series Year	Returns (Points)	Returns (%)
2022	-94	-0.5
2023	-299	-1.6
2024	-426	-2
2025	-500	-2.1

At the end of the December series, rollovers were below their three-month average. Nifty rollovers stood at 72.3%, which are lower than the three-month average of 75.7%.

Foreign Institutions continue to remain net short on the index, with net long exposure continuing to remain at 9%.

Historical data shows that lower FII positioning has generally contributed to healthy returns on the index. Although past performance is no guarantee of future returns.

Series	Long Positions	Subsequent Nifty Move
August 2023	9%	2,579 Points In Next Four Series
November 2023	11%	2,921 Points In Next Two Series
February 2025	11%	2,300 Points In Next Five Series
September 2025	8%	1,435 Points In Next Two Series

FIIs are currently short 1.44 lakh contracts, with client long exposure at 74% and net long 1.18 contracts.

The final F&O series before the Union Budget in February brings with it multiple triggers. Developments around the India-US trade deal will be paramount, while pre-budget consultations, foreign fund flows, and most importantly, the third quarter result updates will be some key triggers for the market this series.