An important thing to keep in mind when tipping: adding a tip to a credit card charge when you sign the credit card slip does nothing. When the credit card slip is presented to you to sign, the transaction has already been processed. Adding an additional amount does nothing. It is possible to process it, but it must be done as a manual charge adjustment and is never done. There are some newer credit card terminals that allow you to enter a tip before processing, but very few places have them. This is true in the BVI as well as in the US.
If you doubt this, you can check it. Add an additional tip to a credit card slip when it is presented to you to sign. Then, later, check your credit card account. The additional amount you added will never show up as a charge to your account.
Bottom line: any tip that you want to add that is not already in the credit card slip must be cash.
Duckfat: Totally incorrect as to the USA and most of the world. Credit card terminals and apps authorize the check amount. Card holders get immediate notification on smartphone showing the check amount authorized. The establishment can then modify the charge for the tip, and the total is what is charged to the cardholder and appears on the monthly statement. Works every time. And actually many places in the world are ahead of the USA in utilizing apps and mobile devices that allow the addition of the gratuity before the card is presented, authorization approved, and charge processed.