Never try to remove a security ink tag from clothing. If you find one has been left on an article of clothing after you get home from the store, return the garment and have a sales clerk remove it. Removing the tag yourself can cause ink to seep onto the clothing. The ink can be removed from white clothes using bleach. Removing security ink from coloured garments is unlikely.
Apply a few drops of isopropyl alcohol to the stain using a cotton swab. Work from the outside of the stain in, so that you do not spread the stain. Blot--do not rub--with a white cloth, pressing down firmly with your hand.
Apply a few drops of nail polish remover with acetone to the stain using a cotton swab, and work on the stain as directed in step 1. Blot the stain again and rinse under warm running water.
Fill a sink or bucket with hot water. Add 1/8 cup liquid laundry detergent and 1/8 cup of colour-safe bleach. For white clothing, use 1/8 cup chlorine bleach instead.
Soak the garment for 30 minutes to one hour if using colour-safe bleach. Soak for only 15 minutes if using chlorine bleach. Chlorine bleach causes damage to fabric fibres after about 15 minutes. Rinse and drain.
Wash the garment in a regular wash cycle, using hot water. Repeat steps 1 through 4 if necessary.
Dab the alcohol and nail polish remover with acetone on an inconspicuous place on the garment, like an inside seam, to test colour fastness. Never put the garment in the dryer or iron it until the stain is gone. Heat will set the stain, making it even more difficult to remove. Stains are easier to remove from natural fibres such as cotton and denim, than synthetics like nylon. Always use a white cloth to blot up stains. You'll be able to monitor your progress as the cloth picks up the stain. Coloured cloths can bleed onto your garment, creating a bigger problem.
Don't use nail polish remover with acetone on acetate or rayon fabric. Acetone dissolves these fabrics.