Flexible Deposit

I think you might be referring to "tip" or "service charge" rather than "flexible deposit", which doesn't seem to be a common food item.

In the United States, it's common practice for restaurants to include a 15% to 20% tip on the total bill, especially if a server has provided good service. This is an optional gratuity that the customer pays at the discretion of the diner, usually as a way to show appreciation for the server's service. Some restaurants may also include a service charge, which is sometimes included in the bill.

Here are some common practices around tipping in the US:

1. The standard tip range is 15% to 20% of the total bill.

2. If the service was poor, it's okay to leave a smaller tip or speak with a manager.

3. Some restaurants may include a service charge, which can range from 10% to 20%.

4. Some restaurants may have a "hidden" service charge, which can be a flat rate of 10% to 15%.

5. If you're eating at a counter or bar, it's customary to leave a 10% to 15% tip.

It's essential to review your bill carefully and understand what's included: do you tip on the total bill, the pre-tax total, or just the food cost? Some restaurants may also have a " tip jar" for the bartenders or other staff members.

If you have any more questions or concerns about tipping, please feel free to ask!