A truck backs into your dock. Your receiving team has no idea what's inside—how many pallets, which SKUs, whether it matches the PO. They'll spend the next two hours counting cartons, scanning barcodes, and reconciling against paperwork. Meanwhile, the driver waits. Your dock stays occupied. And the inventory sits in limbo.

This is warehouse receiving without ASNs. It's slow, error-prone, and expensive.

Advanced Shipping Notices (ASNs) flip this script. When done right, they let you know exactly what's arriving before the truck shows up—cutting receiving time by 50% or more and catching discrepancies before they become your problem.

What Is an ASN and Why Does It Matter?

An ASN is an electronic document sent by suppliers before shipment arrives. It tells you:

What's coming — SKUs, quantities, lot numbers
How it's packed — carton counts, pallet configuration, weights
When it's arriving — carrier info, tracking, expected delivery window
What it references — PO numbers, shipment IDs

Think of it as a digital packing slip that arrives ahead of the physical goods. Instead of your team discovering what's on a truck after it arrives, they can prepare for it—assigning dock doors, staging equipment, and pre-validating against open POs.

The efficiency gains are substantial:

Without ASN → Manual count, line-by-line PO matching, data entry
→ 45-90 minutes per trailer

With ASN → Scan-and-verify workflow, pre-populated WMS data
→ 15-30 minutes per trailer

That's not theory. Warehouses that implement ASN-based receiving consistently report 40-60% reductions in dock-to-stock time.

The Real Cost of Non-ASN Shipments

When a shipment arrives without an ASN (or with an inaccurate one), the downstream impact compounds:

Dock congestion — Manual receiving takes longer, which means trailers sit at doors longer, which means other trucks wait in the yard. At $50-100 per hour in detention fees, this adds up fast.

Labor inefficiency — Your receiving team shifts from verification mode to investigation mode. They're not just confirming what's expected; they're figuring out what arrived.

Inventory delays — Until goods are fully received, they don't exist in your WMS. That's inventory you can't sell, allocate, or ship—even though it's physically in your building.

Error rates — Manual data entry under time pressure produces mistakes. A mis-keyed quantity or wrong SKU creates problems that surface days or weeks later during picking, cycle counts, or customer complaints.

This is why sophisticated warehouses treat ASN compliance as non-negotiable. "No ASN, no dock appointment" isn't punitive—it's operational self-defense.

How to Implement ASN-Based Receiving

1. Define Your ASN Data Requirements

Start by determining exactly what data you need. At minimum:

PO number(s)
SKU/item identifiers
Quantities per SKU
Carton count
Pallet count (if applicable)
Expected delivery date/window

For higher-value or regulated goods, you may also need lot numbers, expiration dates, serial numbers, or country of origin.

Document these requirements clearly. Your suppliers can't send what you haven't specified.

2. Set Up EDI or API Integration

ASNs typically flow through:

EDI 856 → The traditional standard, widely supported by larger suppliers and 3PLs. Works well if you already have EDI infrastructure.

API integration → More flexible for smaller suppliers or custom integrations. Many modern WMS platforms offer supplier portals where vendors can submit ASN data through a web interface.

Flat file uploads → A middle ground. Suppliers upload CSV or Excel files to a secure portal, which your system parses and validates.

The method matters less than the result: ASN data lands in your WMS before the truck arrives.

3. Create Supplier Compliance Standards

Set clear expectations in writing:

Timing — ASNs must be submitted 24-48 hours before delivery
Accuracy threshold — 98%+ accuracy on SKUs and quantities
Completeness — All required fields populated
Consequences — What happens when standards aren't met

Consequences typically escalate:

First offense → Warning and feedback
Repeated issues → Shipment routed to slow lane (manual receiving)
Chronic non-compliance → Dock appointment restrictions or chargebacks

The point isn't to punish suppliers—it's to create clear incentives for accurate data.

4. Build a Validation Workflow

Before a truck arrives, your system should automatically:

Match the ASN to open POs
Flag any SKUs not on the PO
Highlight quantity variances above threshold
Verify the delivery window matches the dock appointment

When everything checks out, the shipment is pre-cleared. Your receiving team knows the ASN is validated before they break the seal.

When something doesn't match, the system generates an exception for review. Handle the discrepancy before the truck arrives, not while it's blocking a dock door.

5. Configure Receiving Lanes

Separate your dock into:

ASN-verified lane — Fast track. Scan pallet labels or carton barcodes to confirm against pre-loaded ASN data. Minimal manual verification.

Non-ASN lane — Slow lane. Full manual count, PO lookup, and data entry. This is where shipments go when suppliers don't comply.

The physical separation reinforces the operational difference—and gives suppliers a visible incentive to get their ASNs right.

6. Train Your Team on the Workflow

For ASN-verified shipments, the process becomes:

Truck arrives → Dock door assigned based on appointment
Verify shipment ID matches ASN
Scan pallet/carton labels
System confirms quantities against ASN
Handle exceptions (damaged goods, miscounts)
Complete receiving and trigger putaway

Train your team to trust the ASN when it's validated—and to escalate quickly when it's not. The goal is smooth flow, not second-guessing the data.

7. Measure and Enforce Compliance

Track supplier performance:

ASN submission rate — % of shipments with ASNs
ASN timeliness — % submitted within required window
ASN accuracy — % matching actual shipment contents

Share these metrics with suppliers regularly. Recognize top performers. Work with underperformers to identify root causes.

Enforcement should be consistent but fair. A one-time error is different from a pattern. The goal is improvement, not gotcha moments.

Common ASN Implementation Mistakes

Starting too big — Don't try to onboard 200 suppliers at once. Start with your top 10-20 by volume. Get the process right, then expand.

Vague requirements — "Send us an ASN" isn't a specification. Document exactly what fields, what format, what timing.

No validation step — If you receive ASNs but don't validate them against POs before trucks arrive, you're missing half the benefit.

Inconsistent enforcement — If some suppliers face consequences for non-compliance and others don't, you undermine the entire system.

Ignoring small suppliers — They may not have EDI capability, but they can use a supplier portal or submit flat files. Don't exempt them entirely.

The Bottom Line

ASNs aren't new technology—they've been part of supply chain operations for decades. But many warehouses still receive a significant portion of shipments blind, simply because they haven't made ASN compliance a priority.

The math is straightforward: If you're spending 60+ minutes receiving a trailer that could be done in 20, and you receive 50 trailers a week, that's hundreds of labor hours and dozens of detained drivers you're paying for unnecessarily.

At Sizelabs, our Parcel AI system integrates with ASN data to further accelerate receiving—automatically capturing dimensions and verifying quantities as goods move through the dock. If you're looking to take your receiving operation from hours to minutes, let's talk about how automated dimensioning and ASN-driven workflows work together.

How to Use ASNs to Speed Up Warehouse Receiving