Periodic vs. Perpetual Inventory Methods

October 03, 2019 by in category Fishbowl Inventory, Inventory Management with
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The Periodic Inventory Method

Back in the Bad Old Days, that is before computers, accountants and business owners had to rely upon the magic inventory equation to calculate cost of goods sold: 

Beginning Inventory + Purchases – Ending Inventory = Cost of Goods Sold for the period 

The value of inventory at any point in time is cost * quantity.  That is the value in the inventory asset account as of the first of the year or our “Beginning Inventory”. 

As you operate throughout the period (month, quarter, year) all inventory purchases are coded to purchases (usually a cost of goods sold account). 

At the end of the period, a physical inventory is performed. Who doesn’t just love physical inventories? The count is then valued to arrive at the “Ending Inventory”.  The company would make an entry to adjust the inventory on the balance sheet and the resultant amount left in the purchases account is the cost of goods sold for the period.

So, depending on how long the period was business owners were flying blind regarding their profitability until the next physical inventory!

This Periodic method was as good as it got before the advent of the “Machine”.

Perpetual Inventory Method

Thanks to our friends, the computer and innovative software publishers such as Fishbowl Inventory, today’s business owner knows how much they made on each sale at the time of sale. 

Fishbowl Inventory tracks each purchase of inventory as a costing layer and the dollars flow to the balance sheet as an inventory asset.  As each item is sold from inventory that transaction is assigned a cost based upon one of the following costing algorithms:

  Terminology   Description
  Average Cost   Total Cost of on-hand inventory divided by the quantity on hand
  Standard Cost   A fixed cost established by the accounting department in co-operation with Operations
  FIFO   First in First Out The oldest costing layer is presumed to be sold first
  LIFO   Last in First Out   The newest costing layer is presumed to be sold first
  FISH   First in Still Here – Just kidding – an old accounting joke

Using a perpetual inventory system gives the business owner instant visibility as to gross profits and is much preferable to the periodic inventory method.

For those of you still stuck in the bad old days, we urge you to check out Fishbowl Inventory or at a minimum QuickBooks Platinum!


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Jeanne Tarazevits
CPA, QuickBooks Maven, Fishbowl Guru

As a Top 100 QuickBooks ProAdvisor and Fishbowl Inventory Super Hero, Jeanne helps businesses change the way they do business by getting their inventory management, accounting and manufacturing systems all working together seamlessly. In providing these services Jeanne draws upon her knowledge as a CPA, her previous experience as an Auditor with Ernst & Young and long-time CFO of a publicly-traded medical device manufacturer, and the expertise gained in the 10+ years she has been working with Fishbowl Inventory.

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