Inventory Management for Beginner Marketplace Sellers: Where to Start

You're Just Starting on a Marketplace — Why Think About Inventory Now?

Many new sellers think: "I only have 5 products, what tracking? I'll keep it in my head."

Three months pass. Now there are 30 products. It's a mess. Excel broke. Unclear how much stock is left and whether you're even making money.

Starting correctly from day one isn't hard. It takes 1 hour. And saves weeks of headaches later.

Key Terms in Plain Language

SKU (Stock Keeping Unit) — a unique identifier for each of your products. If you sell a t-shirt in three colours and two sizes — that's 6 different SKUs, not one product. Each SKU is tracked separately.

Stock levels — how many units of each SKU you have right now. At your warehouse, at the marketplace warehouse, in transit — separately for each location.

Goods receipt — the operation of receiving products from a supplier. You record the date, quantity, and purchase price.

Shipment — sending products out. To a marketplace warehouse (FBO) or directly to a customer (FBS).

WAC (Weighted Average Cost) — sounds complex, but the idea is simple: when you buy the same product at different prices, WAC automatically calculates the average real cost per unit. Example: bought 100 units at 200 ₽, then 50 more at 230 ₽ — WAC is 210 ₽ per unit.

FBO — your product is stored at the marketplace warehouse. You ship a batch, the marketplace handles individual orders.

FBS — products are at your warehouse, you ship each order yourself.

Inventory count — periodic comparison of actual physical stock against what the system shows. Done monthly or quarterly.

Three Most Common Beginner Mistakes

Mistake 1: "I'll remember it in my head"

Your head is a poor database. Works up to about 10 SKUs, then losses start. You either sell what you don't have, or don't realise you should have reordered weeks ago.

Mistake 2: Counting profit from revenue

The marketplace transferred 50,000 ₽ to you — that's not profit. From that you need to subtract cost of goods, shipping to the marketplace, commission, storage, advertising, returns. Real profit might be 5,000 ₽ or even negative.

Without tracking cost price you don't know if you're making money.

Mistake 3: Starting inventory "later when I grow"

"Later" is when you already have 100 SKUs and a burning deadline. Switching from chaos to order is 10 times harder than starting correctly from zero. Every day without tracking is data you'll never recover.

What to Track From Day One

The minimum set for any marketplace seller:

1. Product catalog — each SKU with article number, name, unit of measure, and minimum reorder level.

2. Supplier receipts — every batch: date, quantity per SKU, purchase price, shipping costs from supplier.

3. Marketplace shipments — every FBO delivery or FBS shipment recorded in the system.

4. Current stock levels — the system calculates automatically after each operation.

That's it. Nothing more needed at the start.

Your First 7 Days: Step by Step

Day 1: Register and set up Create your first warehouse — call it "Main warehouse". If you use FBO — create a second warehouse "FBO Ozon" or "FBO WB".

Day 2: Add all products Create a card for every SKU you currently have. Take your time — better to spend an hour doing it right than fixing mistakes later.

Day 3: Enter opening stock balances Count how much of each product you actually have right now. Enter as "opening balance". This is your starting point.

Days 4-6: Record all operations Received goods from supplier → receipt. Sent to WB → shipment. Customer returned → return. Everything in the system on the day it happens.

Day 7: First check Compare system stock against physical stock. If it matches — great, the system works. If not — find the missed operation.

How to Calculate Cost Price Correctly From Day One

Cost price isn't just the supplier price. It's everything you spent to get the product to your warehouse.

Full cost price per unit:

Supplier purchase price
Shipping from supplier to your warehouse (split across all units in the batch)
Packaging and labelling
Shipping to marketplace warehouse

Example: bought 100 units at 150 ₽, shipping 3,000 ₽, packaging 500 ₽. Total spent 18,500 ₽ for 100 units = cost price 185 ₽ per unit.

If you sell for 350 ₽ and WB commission = 80 ₽ — real profit is 85 ₽, not 200 ₽.

When to Add More Complexity

Start with the minimum. Add complexity only when you feel the need:

At the start: receipts + shipments + stock levels. That's enough.

After 3 months: add profit calculation per SKU — see which products actually make money.

After 6 months: turnover analytics — see which products are freezing your cash.

After a year: marketplace integrations, automatic sales import.

Frequently Asked Questions

Should I track stock that's already at WB's warehouse? Yes. Create a separate warehouse "FBO WB" and enter the stock there. This gives you a complete picture across all locations.

What about damaged goods and write-offs? Record as a separate "write-off" operation with a reason. This helps you see real losses.

How often should I do an inventory count? When starting out — every two weeks. Once processes are established — monthly.

Do I need separate accounting software? Warehouse inventory and accounting are different things. Inventory is for day-to-day decisions. Accounting is for taxes. At the start you can run them in parallel independently.

Start Now — It Takes 1 Hour

SelSklad — free inventory management built for Ozon and Wildberries sellers. Unlimited SKUs, warehouses and transactions.

Start for free →