Tipping seamstresses is not standard protocol. That said, anytime a talented seamstress goes above and beyond, offering a gratuity is a thoughtful gesture. A gratuity might be appropriate if the seamstress accepted a large project for you at the last minute — for example, hemming new suit pants the night before your work trip or taking in your party dress the day before your birthday. A gratuity may also be appropriate as recognition for the long hours of skilled stitching that your seamstress has put in altering your wedding dress, which often requires multiple fittings and precise fixes to make your dress perfect. If you do decide to offer a gratuity, first ask if the seamstress accepts gratuities; if they do, offer them an additional 15 percent to 20 percent of the total bill.