Green’s Dictionary of Slang

(Aus./N.Z. Und.) to fail to honour a debt or obligation.

[1921		(con. WWI) N&Q 12 Ser. IX 417: And what of such expressions as [...] ‘lash-up’ (to describe the failure of any organized undertaking: an attack that failed or a manoeuvre that came to grief was always; ‘an absolute lash-up’].
1923		Smith’s Wkly (Sydney) 2 June 21/2: It hurt me to cut-up, even, with such a bungler, but he was working with me and, as I thought, doing his best, so l never ‘lashed’ him.
1935		Thieves Slang ms list from District Police Training Centre, Ryton-on-Dunsmore, Warwicks 6: Lash (to put the lash on): To divide the swag unfairly.
1967		‘Whisper All Aussie Dict.’ in Kings Cross Whisper (Sydney) xxxvi 4/1: lash: To renege on paying a debt.
1982		G. Newbold Big Huey 199: The screws resented Kapua for starting the strike, and the lads resented him for lashing on it. [Ibid.] 250: lash (v) Fail to honour a debt or obligation. From the English legal term laches (negligence).
1984		B. Ellem Doing Time 191: lash: to lose at cards or other gambling, or borrow money, and then not pay up.
1993		Smith & Noble Neddy (1998) 136: They didn’t like my refusal, but I couldn’t give a fuck one way or another. [...] They conned my partner into doing it and he just lashed on them cold [didn’t pay police their share of the proceeds]. So they charged him with armed robbery. [Ibid.] 238: Tony was reluctant to give the cops their whack. He wanted to lash [renege on payment].