The most common way to take inventory in bars and restaurants is with the opening and closing inventory method. Opening refers to the start of a period of time. And closing refers to the end of that same period.

If you take inventory for a bar on the last day of each month, then you can measure your bar's performance for each month time period. If you take inventory on January 31st and again on the last day of February, the 28th, then your opening inventory will be January 31st and your closing will be February 28th.

Using this method, you can track inventory performance during those two dates to find important data like Cost of Goods Sold, Inventory Usage Rate, and more.