The aim of this study was both to analyze prescription errors involving clonazepam and suggest improvements for patient safety. A descriptive and observational study with retrospective data collection was conducted at 30 community pharmacies in Natal city, Rio Grande do Norte state, Brazil. Prescription notifications were analyzed for legible handwriting and completeness. A reviewer committee evaluated patient and purchaser’s identification, pharmaceutical form, dosing regimen, administration route, and prescription by generic name. Among the 313 collected notifications, 44.1 % were legible. A total of 55.91 % had at least one illegible item, 100 % contained incomplete information, and 97.12 % contained one or more abbreviations. The proportion of illegible handwriting related to the patient's identification was statistically significantly and greater than that related to the drug purchaser's identification. This study showed high percentages of prescribing problems, identified potential causes of them, and suggest future research about medication errors in Brazilian community pharmacies.