This study compares AI-generated (ChatGPT and Gemini) and human-written business refusal texts. A genre analysis found that AI-generated texts are formulaic and less nuanced than human-written texts. Applying a rating of professional writing quality, inferential statistics revealed no significant difference in scores between Gemini and human-written texts, but revealed ChatGPT as lower. Human assessors identified authorship of AI-generated texts with an accuracy rate of 68.1%, and human-written texts with 86% accuracy. Key concerns for assessors were tone, relationship, language choice, content, and structure. The findings inform four key areas of focus for teaching business writing in the AI age.