During the period of the Ninth Parliament, which commenced on August 20, 2020 and was dissolved by the Hon. President at midnight on September 24, 2024, there were 19 vacancies of Parliamentary seats according to Article 66 of the Constitution, and accordingly, 16 members have been appointed as new Members of Parliament in 18 occasions.
Accordingly, 241 MPs have represented the Ninth Parliament. Hon. Jayantha Katagoda, who was elected to Parliament from the national list, resigned and Hon. Basil Rajapaksa was appointed in his place. Then the National List Member, Hon. Ajith Nivard Cabral resigned and Hon. Jayantha Katagoda was again appointed to the vacancy. Similarly, for the vacant seat due to the resignation of Hon. Mujibar Rahman, Hon. A.H.M. Fowzie was elected and Hon. Mujibur Rahman was again appointed for the Parliamentary seat of Hon. (Mrs.) Diana Gamage, which was vacant due to a court decision. However, a new MP was not appointed for the vacant Parliamentary seat of Hon. Harin Fernando.
One of the most significant events that captured public attention during this term was the election of Hon. Ranil Wickramasinghe as the 8th Executive President of Sri Lanka following the resignation of the 7th Executive President of Sri Lanka, Hon. Gotabaya Rajapaksa. Thus, 16 new Members of Parliaments have been appointed, including the appointment of a new MP to replace the Parliamentary seat that was vacated by Hon. Ranil Wickramasinghe, who was a Member of Parliament.
| No. | Name of MP and Reason for Resignation | Name of the New MP Appointed for the Vacancy |
| Resignation | ||
| 01 | Hon. Jayanta Katagoda | Hon. Basil Rajapaksa |
| 02 | Hon. Ajith Nivard Cabraal | Hon. Jayanta Katagoda |
| 03 | Hon. Mahinda Samarasinghe | Hon. Lalith Warnakumara |
| 04 | Hon. Basil Rajapaksa | Hon. Dhammika Perera |
| 05 | Hon. Mujibur Rahuman | Hon. A. H. M. Fowzie |
| 06 | Hon. Chaminda Wijesiri | Hon. Nayana Wasalathilake |
| 07 | Hon. Uddika Premarathna | Hon. S. C. Muthukumarana |
| 08 | Hon. Thalatha Athukorala | Hon. Karunaratne Paranavithana |
| Disqualification under Articles 89 or 91 of the Constitution | ||
| 09 | Hon. Ranjan Ramanayake | Hon. Ajith Mannapperuma |
| 10 | Hon. Diana Gamage | Hon. Mujibur Rahuman |
| Expelled from Party Membership | ||
| 11 | Hon. Naseer Ahamed | Hon. Ali Zahir Moulana |
| 12 | Hon. Manusha Nanayakkara | Hon. Bandula Lal Bandaragoda |
| 13 | Hon. Harin Fernando | —– |
| Deceased | ||
| 14 | Hon. Amarakeerthi Athukorala | Hon. Jayanta Samarawickrama |
| 15 | Hon. Sanath Nishantha | Hon. Jagath Priyankara |
| 16 | Hon. H. Nandasena | Hon. M. G. Weerasena |
| 17 | Hon. R. Sampanthan | Hon. Kadiravelu Kugathasan |
| Appointed to the Presidency | ||
| 18 | Hon. Ranil Wickremesinghe | Hon. Vajira Abeywardena |
| 19 | Hon. Anura Kumara Dissanayake | Hon. Lakshman Nipunarachchi |
This Parliament has undergone four prorogations. The first two prorogations were carried out by the former President Hon. Gotabaya Rajapaksa, while the third and fourth prorogations were initiated by former President Hon. Ranil Wickremesinghe. Accordingly, five sessions were held in the Ninth Parliament. The first session lasted from August 20, 2020, to December 12, 2021; the second session from January 18, 2022, to July 28, 2022; the third session from August 3, 2022, to January 27, 2023; the fourth session from February 8, 2023, to January 26, 2024; and the fifth session from February 7, 2024, until the dissolution of Parliament on September 24, 2024.
During these five sessions, Parliament convened for a total of 390 days.