I'd just like to echo the advice of those who say to ask to see pictures of the tattoist's previous cover-up work before you take the plunge - my husband had quite a large (10cm long x 6 cm wide) tatto covered up with a new design, and now that the colours of the new tattoo have faded a bit, you can see most of the original tatto underneath. This was all done about 15 years ago, so no doubt tatto technology has moved on since then, but it would still pay to "shop around" as you would with other purchases.