From Longman Dictionary of Contemporary Englishreport sickreport sickBECMIto officially tell your employers that you cannot come to work because you are ill → report
Examples from the Corpus
report sick• Time allowed 00:20 Read in studio Trade unions at Rover Cars have attacked plans to penalise staff who continually report sick.• Spurs clearly felt the loss of their big centre-back Guy Butters, who had reported sick on the coach journey to Essex. 