Green’s Dictionary of Slang

(US prison) a disciplinary report, stating the offense, time and day the infraction occurred and disposition procedures.

1950		Goldin et al. DAUL 240/1: Write-up, n. (P) A formal report lodged against an inmate for rule violation.
1993		H. Prejean Dead Man Walking 32: Eddie keeps receiving disciplinary write-ups, which land him in the ‘hole,’ a stripped-down disciplinary cell .
2002		J. Lerner You Got Nothing Coming 206: Ringer is ripping up another of Stanger’s write-ups.