📦 How Do I Know Which Dates to Use for COGS Periods When New Stock Arrives?

When new inventory arrives, you’ll need to enter a new COGS period. But how do you know when the old stock runs out and the new batch begins?

Rather than guessing, here are two practical methods to help you determine the correct transition point — both supported by features within SellerLegend.

✅ Option 1: Use the Days of Inventory Metric

Before your new stock arrives at Amazon:

1. Go to Product and Inventory → Products.

2. Locate the product in question.

3. Check the “Days of Inventory” column. This shows how many days you have left before your stock runs out, based on your current sales velocity.

4. Add that number of days to today’s date.

5. Use that resulting date as the start date for your new Cost Period.

Example:

• You have 20 days of inventory remaining.

• Today is April 1st.

• 20 days from now is April 21st.

• Set your next Cost Period to start on April 21st.

📅 Pro Tip: It’s completely fine to create future-dated Cost Periods. SellerLegend will automatically switch to the new COGS when the date arrives.

✅ Option 2: Use a Weighted Average Cost

If you’re unsure exactly when old stock will run out — or if the transition between shipments is gradual — you can use a Weighted Average COGS to smooth the crossover.

Here’s how:

1. Note the number of units remaining from the old shipment.

2. Record the number of units received in the new shipment.

3. Multiply each quantity by its COGS.

4. Add both amounts together.

5. Divide by the total number of units to get your average cost per unit.

Example:

• Old stock: 20 units @ $5 = $100

• New stock: 100 units @ $4 = $400

• Total: 120 units = $500

Weighted Average COGS = $500 ÷ 120 units = $4.17 per unit

To implement this:

• Create a new Cost Period starting on the day the new stock arrives.

• Instead of recalculating every Cost Element to total $4.17:

  • Keep your usual breakdown,

  • Then add a Cost Element labeled something like “Averaging Adjustment” to make up the difference (e.g., add $0.17 per unit).

🔍 Summary

• Use Days of Inventory to estimate when the old stock will run out — ideal for clean batch transitions.

• Use Weighted Average if stock is blended or the cutoff is unclear.

Both methods are fully supported in SellerLegend, and you can set future-dated COGS periods with confidence.

If you have questions or need help applying either approach, don’t hesitate to reach out to our support team!