In a casual workplace jeans are everyday attire and shirts with or without collars are the norm.
Office casual. Women have a wider range of options. Any working woman should have the following staples in her wardrobe. Appropriate business casual outfits for women include a skirt or dress slacks blouse sweater twinset jacket optional and hosiery optional with closed toe shoes. Sandals or peep toe shoes may be permissible in some offices but save flip flops for the weekend.
Most suit jackets or sports jackets are also acceptable attire for the office if they violate none of the listed guidelines. You will rarely see men wearing ties or sport coats in either business casual or casual workplaces unless the employee has a customer or client facing day planned. Casual shirts dress shirts sweaters tops golf type shirts and turtlenecks are acceptable attire for work.