FIFO is our third and final cost flow assumption for inventory costing methods. FIFO stands for “first in first out” so we compute our cost of goods sold using the EARLIEST inventory we have and moving forward in time. DISCLAIMER: I am teaching this from a PERIODIC inventory system perspective, rather than a PERPETUAL perspective. Perpetual systems are MUCH more commonly used in practice, but are MUCH more complex for these problems in class, so for INTRO accounting I use periodic systems to mor