The inventory method, specifically Last-In, First-Out (LIFO) and First-In, First-Out (FIFO), is significant in Form 100 as it is used to determine the cost of goods sold (COGS) for inventory-based businesses. The choice between LIFO and FIFO can impact the taxpayer's net income and subsequent tax liability. LIFO assumes that the most recently acquired inventory is sold first, while FIFO assumes that the oldest inventory is sold first. The difference between the two methods can result in different COGS and, consequently, different net income figures. Taxpayers must choose the inventory method that best represents their business and report it accordingly on Form 100.