Written material provides an important way for services to communicate with patients. Those who require detention under the Mental Health (Care and Treatment) (Scotland) Act 2003 or the Criminal Procedure (Scotland) Act 1995 in Forensic Services within NHS Scotland are usually issued with statutory letters that contain information about their detention. To ensure that letters are readable by patients, templates of such letters were obtained from all health boards in Scotland and analysed using readability indices. Response rate across health boards was 92% (12/13). The results were compared according to readability threshold, types of letters, legal orders and health boards. Between 11.9% and 57.6% of issued letters were found not to be readable. It was also found that there were significant differences in readability across health boards. The study modified the original template of letters, and post-modification readability significantly improved. It may be helpful for patients if NHS Scotland issued such letters with improved readability or introduced a standard template.