Crew gratuity.
A standard 10–15% of the base rate at the end of the trip. How much, when, and how — without overthinking it.
How much
The convention is 10–15% of the base charter rate, paid in cash to the captain at the end of the trip for distribution. 10% if the trip was good; 12% if it was great; 15% for exceptional service or where the crew went materially beyond the contract. For very large yachts (70m+, crew of 15+), 10% is the norm.
When
The last morning, in cash, in an envelope, handed to the captain in private. The captain distributes by formula (longer-tenured roles get a higher share); you don't need to tip individual crew members directly.
What currency
USD or EUR are both fine. Local currency (Croatian kuna, Turkish lira) is acceptable but less appreciated — most crew bank in dollars or euros.
If service fell short
If something material went wrong, talk to the broker before the trip ends. A frank conversation with the captain mid-charter usually corrects it. Withholding gratuity at the end without notice is not the convention; reducing it with explanation is acceptable.