Retail Shop Bookkeeping: Inventory, COGS, and Shrinkage Without the Spreadsheet Nightmare

Almost every retail owner we meet has the same problem: their P&L says they're profitable, but their bank account disagrees. Nine times out of ten, the cause is broken inventory accounting. If you don't book cost of goods sold (COGS) correctly and track shrinkage as a real number, your gross margin is fiction — and you've probably been mispricing items for years.

Why "I Bought It So It's an Expense" Is Wrong

When you buy $10,000 of inventory in March, that's not a March expense. It's an asset sitting on your shelves. It only becomes an expense — COGS — when the item actually sells. Expense it on purchase and your P&L looks brutal in buying months and unrealistically rosy in slow months. Multiply that across a year and you have no idea what your real margins are.

Perpetual vs. Periodic Inventory

You have two real options:

• Perpetual inventory: Every sale automatically reduces inventory and books COGS in real time. Best for shops with a modern POS (Shopify, Square, Lightspeed) and SKUs that matter.
• Periodic inventory: You count inventory monthly or quarterly and book COGS as the change. Simpler, fine for very small shops, but you fly blind between counts.

Most retail shops should be on perpetual. Modern POS systems make it effectively free.

Track Shrinkage as Its Own Line

Shrinkage — theft, breakage, miscounts, return abuse — typically runs 1–3% of revenue for small retail. If you bury it in COGS, you'll never address it. Book it to its own expense line and review it monthly. Suddenly you can see whether a specific store, shift, or product category is the source of the bleed.

Don't Forget Freight-In and Vendor Discounts

Shipping cost to get inventory to you is part of COGS — not a separate "shipping" expense. Likewise, vendor discounts and rebates reduce COGS, not "other income." Get these right and your gross margin actually means something.

Doing Monthly Inventory Closes

Even on perpetual inventory, you should reconcile a section of the shop monthly and the whole shop quarterly. Adjust the books to the count, route the difference to shrinkage, and you have a system you can trust at year-end.

How GuidedLedger Helps Retail Owners

GuidedLedger sets up real inventory accounting tied to your POS, reconciles every channel against the bank, and surfaces shrinkage, returns, and discount drag as their own lines so you finally see what's eating your margin. Learn more on our retail bookkeeping page.