Has there ever been a 12–0 in all competitions?

Yes, 7 times.

The first time: April 4, 1892, West Bromwich Albion beat Darwen (West Bromwich Albion 12–0 Darwen) · Premier League.

The last time: October 26, 1986, Argentinos Juniors beat Talleres (Argentinos Juniors 12–0 Talleres) · Primera Argentina, 39 years ago.

Home wins: 6. Away wins: 1.

Nearby scores

1. 13–0 1 time
2. 13–1 1 time
3. 12–0 7 times
4. 12–1 3 times
5. 11–0 5 times
6. 11–1 6 times

All games

1. October 26, 1986 Argentinos Juniors 12–0 Talleres · Primera Argentina
2. April 29, 1978 Borussia Mönchengladbach 12–0 Borussia Dortmund · Bundesliga
3. April 21, 1909 Nottingham Forest 12–0 Leicester City · Premier League
4. June 21, 1908 Alumni 12–0 Reformer · Primera Argentina
5. May 7, 1905 Quilmes 12–0 Reformer · Primera Argentina
6. June 11, 1903 Flores Athletic 0–12 Barracas Athletic · Primera Argentina
7. April 4, 1892 West Bromwich Albion 12–0 Darwen · Premier League