When it comes to trim, whether you have to sand before restaining depends on its condition and the desired result. If the trim has an existing finish or stain that is in good condition and still adheres well, you may be able to skip sanding if you plan on reapplying a similar shade of stain over it. Instead, clean the trim thoroughly with a mild detergent solution and then proceed with staining directly after drying. However, if there are visible imperfections like scratches, uneven coloration, or peeling finish, it is highly recommended to sand these areas lightly before applying a new coat of stain for better adhesion and achieving a more uniform appearance in your final result.