When Ship Essential ships an order on your behalf, we purchase the shipping label using our carrier accounts (USPS, UPS, FedEx, APC, and others). We then pass the carrier’s shipping charge through to you on your invoice. Because these are third-party carrier charges that we pay on your behalf, they are pass-through and not disputable.

This article explains what you’ll see on invoices, why charges sometimes change after delivery, and how dimensional weight affects label pricing.

At the moment an order ships, our shipping system pulls an estimated rate from the carrier based on:

• Service level (Ground, 2-Day, Priority, etc.)

• Ship-from and ship-to zones

• Package weight

• Box dimensions

• Any carrier rules tied to the service (residential delivery, oversize thresholds, etc.)

That estimated rate is the amount you’ll see billed on the next invoice as the initial label charge.

After the package enters the carrier network, carriers may perform automated audits. This can include:

• Verifying actual billed weight (including dimensional weight rules)

• Confirming package dimensions

• Applying fuel surcharges and other assessorials

• Applying address correction or other exceptions (when applicable)

This audit can happen days or weeks later, sometimes even after delivery.

If the carrier changes the charge (up or down), we pass that adjustment through on a subsequent invoice. You may see this as:

• Carrier adjustment (additional charge), or

• Carrier credit (price adjusted down)

Because the carrier timing varies, adjustments can appear weeks after the original ship date.

The most common reasons:

• Dimensional weight audit (the carrier determines a higher billable weight based on box size)

• Fuel surcharges (vary over time and by carrier/service)

• Address corrections (incorrect or incomplete address details)

• Additional handling / oversize rules (dimensions, packaging type, length + girth thresholds, etc.)

• Service changes (rare, but can happen in exception flows)
  
  

Carriers don’t price shipments only by how heavy they are. They also price based on how much space a package takes up in a truck, plane, or delivery network. That’s where dimensional weight comes in.

Carriers charge based on the billable weight, which is the greater of:

• Actual weight (what the package weighs on a scale), or

• Dimensional weight (a calculated weight based on box size)

So a large, lightweight box can cost more than a smaller, heavier box.

Most carriers use a formula like:

Dimensional Weight = (Length × Width × Height) ÷ DIM Divisor

• Dimensions are typically in inches

• The DIM divisor varies by carrier and service level, and it can change

• Carriers also apply rounding rules (for example, rounding up to the next whole pound)
  

Example:

A box that is 16” × 12” × 10” has a volume of 1,920 cubic inches.

If the carrier’s divisor for that service is 139, the DIM weight is about 13.8, which typically rounds up to 14 lb.

If the actual weight is 6 lb, the carrier charges as if it is 14 lb.

Because DIM weight depends on dimensions, the box size can materially change label cost, even when the items weigh the same. That’s why we focus on using an appropriately sized box for each order.

Our packing approach is designed to avoid unnecessary DIM impact:

• We use right-sized packaging whenever possible

• We select the best box size available for the order

• We rely on accurate product weights and packaging data to rate shipments correctly

• We follow carrier-compliant packing standards so packages move smoothly through audits

If product dimensions/weights or packaging rules change on your side (new assortment, new kits, heavier inserts, different folding), that can also change shipping costs even when service level stays the same.

Because carrier label charges are pass-through costs that we pay to the carrier on your behalf, they are not disputable on our invoices.

Typically, shipping-related charges fall into two buckets:

1. Initial label charges: estimated at ship time from the carrier rate engine

2. Carrier adjustments/credits: posted later if the carrier audits and changes the charge

This is normal carrier behavior across major networks, and it is why shipping costs can show up in more than one billing cycle.

Why didn’t we know the “final” cost at ship time?

Carriers will often audit dimensions, weight, and surcharges after pickup.

Can adjustments be credits too?

Yes. Carriers sometimes adjust charges down, and we pass those credits back to you.

Does dimensional weight apply to every shipment?

It depends on carrier and service, but DIM rules are common across major parcel networks.

How can we reduce DIM impact?

Right-sizing packaging, avoiding oversized void fill, and keeping product weight/dimension data accurate are the biggest levers.