The Election Commission announced on September 7, 2026, that by-elections would be held on October 6 for Assam's Nagaon Lok Sabha constituency and five Assembly seats. Akashvani identified the Assembly constituencies as Madurantakam and Dharapuram in Tamil Nadu, Rejinagar and Nandigram in West Bengal, and Thattanchavady in Puducherry. Its announcement report gave September 16 as the nomination deadline and October 9 as the counting date.
In Tamil Nadu, the commission's September 9 gazette notices identify the resignations of K. Maragatham Kumaravel and P. Sathyabama as the causes of the Madurantakam and Dharapuram vacancies. Both seats became vacant on May 25 and are reserved for Scheduled Castes. The notices prescribed polling from 7 am to 6 pm and required the elections to be completed before October 11.
The West Bengal contests followed the resignations of Suvendu Adhikari from Nandigram and Humayun Kabir from Rejinagar, The Economic Times reported on September 7. Both politicians had won two constituencies in the Assembly election: Adhikari won Nandigram and Bhawanipur, while Kabir won Rejinagar and Nowda. Citing the commission's release, the newspaper reported September 17 for scrutiny and September 19 as the last date for withdrawals.
Puducherry's September 9 notification records that N. Rangasamy's resignation left Thattanchavady vacant on May 17. It set the same September 16, 17 and 19 stages for nominations, scrutiny and withdrawals, followed by October 6 polling from 7 am to 6 pm. The territory's published notice therefore supplied both the legal reason for this Assembly contest and the detailed timetable following the national announcement.
Nagaon's official notice, also dated September 9, records a March 20 vacancy following Pradyut Bordoloi's resignation. It prescribed voting from 7 am to 5 pm on October 6, an hour earlier than the notified closing time in Puducherry. Although the two contests shared nomination and polling dates, their voting windows were not identical. The Assam notification likewise required completion of the election before October 11.
