A by-election was held for the New South Wales Legislative Assembly electorate of Cumberland South Riding on 12 June 1856 because William Manning resigned in May 1857 due to ill-health.[1]
| Date | Event | |
|---|---|---|
| 18 May 1857 | William Manning resigned. | |
| 21 May 1857 | Writ of election issued by the Speaker of the Legislative Assembly.[2] | |
| 9 June 1857 | Nominations | |
| 12 June 1857 | Polling day | |
| 16 June 1857 | Return of writ |