Green’s Dictionary of Slang

1. (orig. RAF) to completely destroy something, so that it is beyond all hope of repair; occas. of individuals (see cite 1955).

1918		‘The 100 Squadron Lament’ in C.H. Ward-Jackson Airman’s Song Book (1945) 61: We wrote off his best drome.
1931		Flight Jan. 80/1: The D.H.37 [...] got down without much damage. The D.H.9.C., which was acquired later, was less fortunate, and was written off in a forced landing .
1943		Bayler & Carnes Last Man Off Wake Island 86: Write off one Jap destroyer, Walt!
1955		C. John Nothing to Lose 225: [A] few of the leading men penetrated into the village, but the rest were completely written off.
1960		A. Buzo Front Room Boys Scene i: Don wrote off his sprite. [...] Took a hairpin at eighty and ruptured himself on the dashboard.
1977		Car and Driver XXIII 107: He hit a tree and wrote off the car, the engine lying completely separated in the road!
2001		N. Barlay Hooky Gear 22: Wha she done for me except get sarky with her tits, put sackloads of kuf up her snout an write off 2 previous pink Vitaras?
2008		J. O’Reilly Wife in the North 133: We wrote off the car [...] We’re fine. I broke a rib, that’s all, and your father is a bit bruised.

2. to give up on.

1947		A.C. Wann ‘Growing up in Chad Street’ in Lehmann Penguin New Writing No. 30 (1947) 105: The dog decided to write the cat off and gathered up speed for a rush at me.
1961		‘N.W. Clerk’ A Grief Observed 24: The specifically maternal happiness must be written off.
1977		Ben-Veniste & Frampton Stonewall 90: Only a few people could tell us anything about Nixon’s role in the cover-up. Haldeman, Ehrlichman and Mitchell could be written off.
1980		G. Liddy Will 53: I wrote off the testing fee and filed the report.
1994		(ref. too 1923) Calt I’d Rather Be the Devil 76: Trafficking in bottled whiskey, the Southern barrelhouse became a casualty of Prohibition, as did, apparently, the northern barrelhouses [. . .] and were already written off, in 1923, as ‘a thing of the past.’.
1989		L. Aparvary Legionnaire’s Journey 52: I know only too well that many legionnaires are troublemakers, but please don’t write us all off on that basis .
2007		B. Coleman Check the Technique 23: ‘[A]fter a couple of years, the label had just written them off’.