Methods and analysis: All public somatic and psychiatric hospitals in Denmark (n=30) were invited to participate in the trial. Twenty-three hospitals (77%) (3 university hospitals, 5 psychiatric hospitals, and 15 general hospitals) agreed to participate and to be randomised to one of the trial clusters. Eleven hospitals will receive announced surveys (control group) and 12 hospitals will receive unannounced surveys (intervention group).We hypothesise that hospitals receiving unannounced surveys will be rated as less successful than hospitals receiving announced surveys, defined as meeting less compliance with accreditation standards and performance indicators. Nine experienced surveyors employed and educated by The Danish Institute for Quality and Accreditation in Health Care (IKAS) will be responsible for conducting the surveys according to an abbreviated version of the current Danish periodic survey. The outcome is compliance with indicators reflecting organisational performance. Compliance will be analysed using logistic or linear regression analysis with random effects, contingency tables, and Pearson's chi-squared test or Fishers exact test, whichever is most appropriate.