Inventory how-to

How to manage inventory with a 3PL

Managing inventory with a third-party logistics provider (3PL) means you still own the forecasting and reordering decisions, but the 3PL handles physical receiving, storage, and shipping.

Short answer: Managing inventory with a third-party logistics provider (3PL) means you still own the forecasting and reordering decisions, but the 3PL handles physical receiving, storage, and shipping. You need clean feeds in both directions: stock levels coming from the 3PL into Shopify, and purchase orders going from you to your suppliers (and sometimes to the 3PL as the receiving location).

Keep one source of truth for stock levels

Your 3PL's warehouse system holds the real, physical count. Shopify needs to reflect that count closely, usually through an automated sync or EDI feed from the 3PL, or a manual update if your volume is low. If the two numbers drift apart, your reorder decisions and your storefront availability will both be wrong. Set a routine, even if it is weekly, to check that Shopify on-hand matches what the 3PL reports.

Decide who receives purchase orders

When stock arrives at the 3PL instead of your own location, someone still has to record the receipt, including partial shipments, so your on-hand numbers update. This can be the 3PL (if they report receipts back to you) or your own team checking in against the PO once the 3PL confirms arrival. Either way, write down the process so receiving does not get skipped when you are busy.

Account for the 3PL's own lead time

A 3PL adds a step between "stock arrives" and "stock is sellable," because they may need time to check in, shelve, and process inbound shipments before it counts as available. Add this processing time to your supplier's lead time when you calculate your order-by date, rather than treating supplier lead time as the whole story.

Watch for timing gaps in reporting

Some 3PLs update inventory counts once a day or on a batch schedule, not in real time. If your sales are fast relative to that update frequency, you can oversell before Shopify reflects a true stockout. Build a small buffer into your safety stock to cover this reporting lag, separate from the safety stock you hold for lead time variability.

Step by step

  1. List your 3PL's inbound processing time and add it to each supplier's lead time for order-by date calculations.
  2. Set up or confirm an automated inventory feed between the 3PL and Shopify, or a manual update schedule if automation is not available.
  3. Agree with your 3PL on who logs receipts (including partial deliveries) and how fast that happens after physical arrival.
  4. Add a small safety stock buffer to cover any delay between the 3PL's physical receipt and Shopify's updated count.
  5. Reconcile Shopify on-hand against the 3PL's reported count on a fixed schedule, such as weekly.
  6. Document the full flow from PO sent to supplier, to 3PL receiving, to Shopify stock update, so anyone on your team can follow it.

Worked example

Say your supplier's lead time is 10 days, and your 3PL takes 2 days to check in and shelve a shipment after it physically arrives. Your effective lead time for reorder calculations is 12 days, not 10. If you sell 6 units a day and want 5 days of safety stock on top of that 12-day lead time, your reorder point is 6 x (12 + 5) = 102 units. If the 3PL's inventory feed only updates once daily, you might add 1 extra day of safety stock to cover units sold before the feed refreshes, bringing your safety days to 6 and your reorder point to 6 x (12 + 6) = 108 units.

How SteadyShelf helps

SteadyShelf can use your 3PL's reported lead time and any extra processing days as the lead time and safety days inputs for its order-by date and quantity suggestions, and it receives stock (including partial) into Shopify once you confirm it. It does not connect to or sync directly with 3PL warehouse systems, so you still need your own feed or manual process to keep Shopify's stock count accurate, and it does not manage multi-location or per-warehouse forecasts.

$29/month flat, unlimited products and suppliers, 30-day free trial. Run the numbers now with the free reorder point calculator.

SteadyShelf is launching on the Shopify App Store. Join early access to get the install link first.

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FAQ

Can SteadyShelf place orders directly with my 3PL?

No. SteadyShelf drafts purchase orders and emails them to the suppliers you set up, based on lead time and safety days you enter. If your 3PL needs its own notification of incoming stock, you handle that separately, since SteadyShelf does not integrate with 3PL systems.

How do I handle inventory if my 3PL only updates stock counts weekly?

Add extra safety days to your reorder point calculation to cover the gap between a sale happening and the 3PL's count catching up, since a full week of lag is a meaningful amount of time for most sales velocities. You can enter this buffer directly as safety days in SteadyShelf's per-SKU settings.

Let SteadyShelf do this math for every SKU

Order-by dates per supplier, seasonal forecasts and draft POs for your Shopify store. $29/month after a 30-day free trial.

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