There are a few different ways to categorize expenses, and shipping could fall under a few different categories depending on how you track your expenses. Here are a few possibilities for where shipping could be categorized:
If you track your expenses by department, then shipping would likely fall under your "operating expenses". This would include all the costs associated with running your business, like rent, utilities, payroll, and shipping.
Another possibility is to have a separate category just for shipping expenses. This would include all the costs associated with shipping, like postage, packaging, and shipping insurance.
If you track your expenses by product, then shipping would likely fall under your "inventory expenses". This would include all the costs associated with acquiring and storing inventory, like raw materials, manufacturing costs, and shipping.
There is no right or wrong answer for where shipping should be categorized. It depends on how you track your expenses and what makes the most sense for your business. Talk to your accountant or financial advisor to figure out what system would work best for you.