Free drinks are the most dangerous thing behind the bar
Not for the guest. For you.
Giving away a drink is the one action in this job that is simultaneously expected of you, good for business, a normal part of the culture, and the most common route to being walked out. Every one of those is true at the same time, and the difference between the good version and the fatal version is entirely about whether it was authorised and recorded.
The rule underneath everything in this lesson: a free drink that is rung in is hospitality; a free drink that is not rung in is missing inventory. No manager reviewing a report can tell the second one from theft, and most will not try.
The four kinds and what separates them
Comp. A drink given away deliberately, usually to fix a problem — a long wait, a mistake, an unhappy guest. In most houses this needs a manager, or you have a defined allowance. It is rung in and marked as a comp against a reason code.