In a B2B shop, shipping costs are not a footnote but a margin item. Anyone selling a pallet of insulation, a bundle of profile tubes or a mesh box of spare parts is not sending a parcel but a consignment with weight, volume, loading metres and delivery conditions. Many shops still store one flat rate that applies across the entire catalogue. That is expensive in both directions: on bulky goods the flat rate eats into contribution margin, on small consignments it discourages the order. 40 percent of shoppers who abandon a checkout cite excessive extra costs such as shipping, taxes and fees as the reason (Baymard Institute). This article shows how freight logic can be modelled as a rule set and where a connection to ERP and forwarder data makes the difference.
Key takeaways
- Above roughly 31.5 kilograms per package unit (project experience) parcel shipping ends and the consignment moves into groupage freight with its own tariffs. One flat rate across the catalogue subsidises expensive consignments and looks excessive on small orders.
- What counts is chargeable weight: the higher of gross weight and weight derived from loading space used. Common conversions are one cubic metre to about 333 kilograms and one loading metre to roughly 1,750 kilograms. Without a stacking factor, the rules assume the worst case.
- German truck tolls apply from 3.5 tonnes gross vehicle weight, the infrastructure rate reaches 15.5 cents per kilometre and the CO2 rate up to 16.2 cents per kilometre (Federal Trunk Road Toll Act). Surcharges belong in the system versioned with a validity date.
- Free-freight thresholds and negotiated rates sit on the customer group or account and are read from the leading ERP instead of maintained twice. Incoterms 2020 comprise 11 rules (International Chamber of Commerce); the agreed term reads identically in store and invoice.
- Standard cases are calculated by the store's rule set, exceptions queried live: dangerous goods, oversize items, foreign zones. If the interface stays silent, a short timeout falls back to the rule value plus a note that final freight comes with the order confirmation.
- Base freight and every surcharge appear as separate cart lines before checkout, and each partial delivery or return references the original freight line. When the display differs from the carrier invoice, the cause usually sits in weight, dimensions or stacking factor.
Why flat rates fail in B2B shipping
The difference between parcel shipping and forwarding freight starts with the individual package. In parcel networks the scale ends at around 31.5 kilograms per package with most providers (project experience); anything above that moves into groupage or part-load transport with its own pricing logic. Official statistics show how large that segment is: German trucks carried around 2.8 billion tonnes of goods in 2025 (Federal Statistical Office of Germany), compared with 328 million tonnes by rail (Federal Statistical Office of Germany). Anyone selling building materials, drive technology, chemicals or electrical installation material is also selling transport – and transport follows different rules than a fixed amount per order.
A flat rate is a mixed calculation across very different consignments. It works as long as the real basket matches the calculated average. In B2B wholesale that is rarely the case: one customer orders five kilograms of small parts, the next two pallets taking up 0.8 loading metres, the third a six-metre profile rail that only fits lengthways on the truck. Pricing all three cases at the same amount means subsidising the expensive consignment with the cheap one while losing the orders where the flat rate looks disproportionate. How much the checkout decides at this point is described in the article on B2B checkout optimisation.
Parcel limit
Above roughly 31.5 kilograms per package, parcel shipping ends. The consignment moves into groupage transport with its own tariff structure.
Bulky and oversized goods
Tubes, profiles, panels and window elements create handling effort that cannot be read from the weight alone.
Palletised goods
Euro pallets, industrial pallets and one-way pallets occupy different floor areas and therefore different shares of the freight cost.
Weight versus volume
Light, voluminous goods are charged by volume, heavy compact goods by weight. The higher of the two values sets the price.
Loading metres
Non-stackable consignments occupy the full loading height. The loading metre then becomes the leading figure in the calculation.
Dangerous goods
Items subject to ADR require approved packaging, marking and transport documents, and they trigger their own surcharges.
The flat rate is a silent margin item
The calculation logic behind a freight rate
Forwarding tariffs work with a chargeable weight. That is not necessarily the weight on the scale but the higher of two values: the actual gross weight and the weight derived from the loading space occupied. This conversion prevents light, voluminous goods from occupying loading space at a weight-based rate. Rebuilding that logic in the shop requires four pieces of data per item or packaging unit: weight, dimensions, stackability and packaging type.
- Gross weight – net weight of the goods plus packaging, pallet and load securing. It arises at packaging unit level, not at single piece level.
- Volumetric weight – the volume of the consignment converted with the factor agreed in the tariff. In groupage, a conversion of one cubic metre to around 333 kilograms is common.
- Loading metres – the loading length occupied across the full internal width of the trailer of about 2.4 metres. The key figure as soon as a consignment cannot be stacked.
- Stacking factor – whether and how often a pallet may be stacked over. It decides whether a consignment costs half or the full loading height.
- Minimum freight and small quantity surcharge – the floor below which a consignment does not get cheaper, because collection, handling and delivery cause fixed costs.
The loading metre formula in three steps
The example shows why stackability in the item master is not a detail. If a consignment may be stacked over, many tariffs halve the loading metres applied. Where the value is missing, the rule set calculates the less favourable case for safety reasons – and the shop displays freight above what the forwarder later invoices. The small quantity surcharge behaves similarly: it is not a penalty but the difference to the minimum freight, and it belongs in the calculation as a rule rather than in a price list as an amount.
| Calculation step | Flat rate in the shop | Rule-based freight logic |
|---|---|---|
| Basis | one amount per order | chargeable weight per consignment |
| Volume | not considered | volumetric weight and loading metres |
| Stackability | not modelled | stacking factor per item or packaging unit |
| Small consignments | cross-subsidised | minimum freight and small quantity surcharge |
| Surcharges | priced in as a lump sum | calculated per trigger as a rule |
| Customer terms | rarely differentiated | free freight threshold per customer group |
| Traceability | a number without derivation | an audit trail per order line |
Surcharges that are often missing in the shop
A considerable share of cost movement in road freight sits not in the base tariff but in surcharges. In Germany, the truck toll applies to vehicles with a technically permissible gross mass of more than 3.5 tonnes (German federal trunk road toll act, section 1); craft business vehicles up to 7.5 tonnes are exempt under certain conditions (German federal trunk road toll act, section 1). The toll rate is composed of partial rates for infrastructure, air pollution, noise and carbon dioxide (German federal trunk road toll act, section 3). For vehicles above 18 tonnes with four or more axles, the infrastructure rate alone is 15.5 cents per kilometre (German federal trunk road toll act, annex 1), while the CO2 rate reaches up to 16.2 cents per kilometre depending on emission and weight class (German federal trunk road toll act, annex 1). Toll obligation and enforcement sit with the Federal Office for Logistics and Mobility (BALM).
The second major driver is energy. The German road haulage association BGL publishes monthly diesel price information for bulk buyers and filling stations, which serves as a reference for cost element clauses in transport contracts (BGL). Its industry cost model is published by the 20th or 21st of the following month and shows personnel, fuel, toll, vehicle costs, insurance and administration separately (BGL). In parallel, official price statistics show that producer prices for services rose by 2.4 percent year on year in the first quarter of 2026, with the index at 113.5 (Federal Statistical Office of Germany). Anyone who writes surcharges as a fixed number into a text field has to track that movement manually – and experience shows it happens late.
| Surcharge | Typical trigger | Modelled as a rule |
|---|---|---|
| Toll and energy surcharge | tariff change, index level, distance | percentage uplift on base freight with a validity date |
| Island and special zone | postcode in an island or remote zone | zone assignment via a postcode table instead of manual entries |
| Tail lift | no loading ramp at the delivery address | option in the checkout, pre-filled from the address master data |
| Notification call | delivery announcement requested | optional service with a stored fixed amount |
| Fixed date and time slot | specific day or narrow time window | uplift per service level, selectable in the cart |
| Dangerous goods | ADR marking on the item | derived automatically from the item master, with a quantity threshold |
| Small quantity surcharge | consignment below the minimum freight | difference to the minimum freight instead of a fixed amount |
The form of modelling is decisive. A hand-maintained table of surcharge amounts ages with every tariff round and is hard to verify. A rule, by contrast, describes trigger, calculation method and validity period, and therefore supplies the reasoning as well. Especially in B2B trade with building materials and in technical trade, this difference decides whether the freight shown in the shop matches the forwarder invoice.
Version surcharges instead of overwriting them
Modelling customer-specific freight terms
In B2B, freight is part of the commercial terms. It is negotiated like price, payment term and discount, and therefore rarely applies identically to all customers. Where tiered and customer-specific prices are already differentiated – the basics are described in the article on price lists and tier pricing in Shopware – the freight condition should be anchored in the same place instead of in a second structure maintained in parallel.
Free freight threshold per group
The net value from which freight is waived is a matter of negotiation. The threshold belongs to the customer group or the individual account, not to a global setting.
Terms from the ERP
Negotiated freight rates sit in the leading system. The shop should read them instead of maintaining them a second time and letting both versions drift apart.
Customer collection
Collection at the plant or warehouse is a shipping method of its own with its own price line, often combined with a time slot, a collection number and a contact person.
Ex works delivery
Delivering ex works shifts cost and risk to the buyer. The agreed clause belongs in the order confirmation, the delivery note and the invoice.
Drop shipping
When the upstream supplier delivers directly, separate freight costs arise per partial consignment and have to be calculated and shown separately.
Partial deliveries
When an order is split, every partial delivery needs a traceable freight line – including the question of whether freight applies once or per consignment.
As soon as deliveries cross a border, the agreed delivery clause becomes the central variable. The Incoterms 2020 rules of the International Chamber of Commerce comprise 11 clauses, of which 7 apply to any mode of transport and 4 exclusively to sea and inland waterway transport (International Chamber of Commerce). They have applied since 1 January 2020 and were developed by around 500 experts from more than 40 countries (International Chamber of Commerce). For the shop this means the clause belongs to the customer or order record, affects the freight line and has to appear in the order confirmation. What such a data handover looks like technically is shown in the article on ERP integration in B2B e-commerce.
- Who pays? Customer group, individual account or framework agreement – the source of the condition has to be unambiguous, otherwise chance decides.
- From when is freight waived? Net goods value, weight or quantity as the threshold, with a clear statement on whether surcharges count towards it.
- Which clause applies? Ex works, delivered free or an Incoterms rule – with the same statement in the shop, the order confirmation and the invoice.
- Which shipping method is permitted? Forwarding, parcel, customer collection or drop shipment, released differently depending on assortment and customer.
- What happens with partial quantities? Freight per partial delivery or once for the whole order – this rule decides later credit notes.
Technical implementation between rule set and live lookup
The architecture follows a simple division of labour: the standard case is calculated in the shop, the exception is queried live. That keeps the checkout fast and the number reliable. In a B2B portal with many recurring orders, a well-maintained rule set covers the majority of consignments in our experience; the remaining cases justify the effort of a live lookup.
- Rule set in the shop – zones, weight brackets, loading metre conversion, surcharges and free freight thresholds as a versioned rule set. It calculates without an external call and reproduces the same number reliably.
- Live lookup in the ERP or with the forwarder – for exceptions such as dangerous goods, oversize, foreign zones or individually agreed special rates. The lookup returns an amount plus a reference to the calculation basis.
- Caching – keep results per combination of zone, weight bracket and service level for a defined period. This relieves the interface during basket changes and keeps the checkout responsive.
- Fallback – a timeout in the low single-digit seconds, then the rule value from the shop plus a clear note that the final freight will be confirmed with the order confirmation. The order remains possible and the statement remains honest.
- Display before and after login – without login, a traceable example calculation or a note about customer-specific terms; after login, the actual condition including free freight threshold and surcharges.
What happens when the interface stays silent?
Freight cost and delivery date belong together: both figures come from the same data situation and are assessed jointly by purchasing. How stock and dates can be brought into the storefront reliably is described in the article on real-time availability and delivery times. Anyone deciding on the system architecture in parallel will find the trade-off between an integrated and a decoupled setup in the article on the headless and composable commerce decision – in both variants, freight logic belongs in a separate, testable service.
A checkout should not display a figure that the invoice later corrects. A reasoned range with a clear reservation costs less trust than false precision.
Showing freight in a legally and commercially clean way
In a closed B2B area, net prices are common as long as the shop is clearly aimed at business customers and access is designed accordingly. German price indication rules address offers to consumers, so shops with a mixed audience need a clear separation of presentation. The specific setup belongs to your own legal review – this article does not replace legal advice. As with other transparency duties in the shop, for instance the labelling of AI functions from August 2026, the obligation concerns the presentation and not only the process behind it.
- Shipping costs before order placement – base freight and surcharges appear in the cart before the order button is pressed, not only in the order confirmation.
- Consistent net or gross logic – freight line, goods value and tax statement follow the same presentation so that document totals add up.
- Delivery terms in the terms and conditions and the order confirmation – clause, transfer of risk and cost allocation stated identically in both places.
- Surcharges itemised – toll, island, tail lift or fixed date delivery as separate lines instead of an anonymous uplift on base freight.
- Communicate deviations actively – when the real freight differs from the display, the information belongs before the invoice, not on it.
- Document the calculation basis – store the rule version, tariff and surcharge version per order so that every line can be explained later.
With dangerous goods, packaging is added to the picture. The Federal Institute for Materials Research and Testing tests and approves design types of dangerous goods packaging such as drums, canisters, boxes and intermediate bulk containers, and monitors manufacturing (BAM). Approved packaging carries a UN marking that documents compliance with the European ADR agreement and the UN recommendations (BAM). For the shop this means ADR-relevant items need a flag in the item master, a rule for the dangerous goods surcharge and a check on whether a given basket combination may be shipped together at all.
No surprises on the invoice
Partial deliveries, back orders and return freight
A B2B order rarely stays a single consignment. Stock items go out immediately, drop-shipped items come from the supplier, a remainder follows later. So that shop and ERP do not drift apart, each of these movements needs an unambiguous freight rule and its own document line. Without it, two truths emerge: the freight shown in the shop and the freight posted in the ERP.
Partial delivery
The rule defines whether freight applies once per order or per consignment. With drop shipments, separate calculation is usually the more realistic model.
Back order
Real transport costs arise for the remainder of an order. Whether they are charged or absorbed as a service commitment is a commercial decision – and it belongs in the rule, not in the individual case.
Return freight
Who pays for the return depends on the reason. Defects, incorrect deliveries and goodwill returns lead to different cost bearers and different documents.
Returns require the most reconciliation, because goods value, freight and credit note can diverge. How the process can be modelled in a structured way is described in the article on the B2B returns and RMA process. For freight calculation the principle is: every credit note needs a reference to the original freight line, otherwise a difference remains at month end that nobody can resolve.
Checklist for troubleshooting freight calculation
When freight in the shop deviates from the forwarder invoice, the cause usually sits in master data rather than in the tariff. The following list works as an order of inspection before new tariffs or a new interface are considered.
- Weight maintained on the item, split into net and gross weight per packaging unit
- Packaging unit and outer carton stored so that an order quantity turns into a real consignment structure
- Dimensions available per packaging unit so that volumetric weight and loading metres can be calculated
- Stacking factor set instead of assuming one value for the entire catalogue
- Postcode and zone table up to date, including island and special zones
- Surcharges versioned with a validity date instead of overwritten
- Free freight thresholds checked per customer group, including their interaction with discounts
- Minimum freight and small quantity surcharge stored as a rule, not as a single amount
- ERP terms read rather than maintained a second time in the shop
- Fallback and timeout of the live lookup tested, including the display text in the cart
- Partial deliveries, back orders and return freight posted with a reference to the original line
The route to a reliable freight display rarely starts with technology but with an inventory of existing terms: which tariffs, surcharges and special agreements apply today, who maintains them and in which system do they sit? That inventory produces the rule set for the standard case and the list of cases that require a connection to ERP and forwarder data. After that, the question of what the checkout displays is no longer an estimate but a calculation with a traceable derivation.
Sources and studies
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