The liquor by the drink licensee must collect an excise tax equal to 5% of the gross proceeds of the sales of liquor by the drink and remit it to the SCDOR. It does not matter if the liquor is poured from a minibottle or from a big bottle. Sales tax, which must also be collected and remitted to the SCDOR, is not part of the gross proceeds.
For example, on a $5.00 drink in a county with a 6% sales tax:
$5.00 x .06 = .30 sales tax
$5.00 x 5% liquor by the drink tax = .25
Total cost to the customer = $5.55
If the operator wishes to sell the drink for $5.00 total, the taxes can be backed out as follows: 6% sales tax + 5% liquor by the drink tax = 11% total tax. $5.00 / 1.11 x 11% = $0.50 total tax. This would be allocated as follows: 5/11 x .50 = $0.23 for liquor by the drink tax; 6/11 x .50 = $0.27 for sales tax. If you decide to include the sales tax and excise tax in the listed price of the drink, your signs and menus must say that. In addition, as is the case with sales tax, "gross proceeds" would include any mandatory gratuity, and you must include that amount when computing the sales tax and the liquor by the drink tax.