The officer, who has not been named by the force, was subject to a misconduct hearing, late last month.
The officer accepted failing to record a victim's allegation of rape on the South Yorkshire Police systems and also failing to adequately investigate the allegations of rape and sexual assault.
A third allegation - that the officer failed to take appropriate action to safeguard the victim from future harm from the alleged perpetrator - was proven at the hearing.
The misconduct panel stated the officer's conduct amounted to misconduct in relation to meeting the police officer duties and responsibilitie's code of ethics, accountability and objectivity.
A South Yorkshire Police spokesman said: "The chair decided that the most appropriate outcome was a final written warning."