Each Colissimo offer is based on a precise dimensional specification. Exceeding a length or weight limit does not simply incur an additional cost: the package may be refused at the counter, returned to the sender, or redirected to another pricing offer. Understanding these constraints before packaging avoids costly back-and-forths, especially since the regulatory adjustments that came into effect in 2026.
Volumetric weight and actual weight: the rule that determines the Colissimo rate
La Poste charges for a Colissimo based on the actual weight of the package, capped at 30 kg for mainland France, Monaco, and Andorra. This 30 kg limit applies to both packages dropped off at post offices and those shipped online.
For bulky but lightweight shipments, another parameter comes into play. When the package exceeds certain cumulative dimensions, La Poste applies a “bulky” surcharge. This surcharge does not depend on weight but on the size of the package: it penalizes the volume occupied in the sorting and transport chain.
A detailed guide on Colissimo package dimensions according to La Poste explains the exact thresholds beyond which this additional charge applies and the concrete consequences of exceeding them.
Maximum Colissimo dimensions for shipments within mainland France
The main constraint concerns the maximum length of the longest side. For a standard Colissimo in mainland France, this length must not exceed a threshold set by La Poste. Beyond that, the package is either refused or reclassified into a “non-standard” category with an additional rate.
The total perimeter of the package (length + double the width + double the height) constitutes the second criterion. This calculation, often overlooked, traps senders who comply with the maximum length but neglect the cumulative dimensions.
For mailbox shipments (Colissimo without signature), the constraints are tighter. The thickness of the package must fit into a standardized mailbox, which requires staying under a few centimeters in thickness. In practice, this leads to flat packaging like rigid envelopes or thin postal boxes.
Ready-to-send packaging formats
La Poste sells pre-paid packaging whose dimensions are calibrated to stay within accepted limits. These boxes and envelopes include postage directly, eliminating the risk of miscalculating dimensions.
The most common formats cover three sizes:
- Flat envelope for thick documents or lightweight textiles, suitable for mailbox delivery
- Medium-sized postal box, designed for items like books, small electronics, or accessories
- Larger reinforced box, intended for fragile items requiring padding
Choosing a pre-paid packaging guarantees dimensional compliance, but the total weight (contents + packaging) still needs to be monitored.
Overseas and international shipments: different dimensional thresholds
Colissimo shipments to the DOM, COM, and international destinations are subject to dimensional constraints distinct from those applied in mainland France. Weight limits vary depending on the destination area, and some destinations cap the weight at less than 30 kg.
The allowed cumulative perimeter also differs by area. For overseas territories, La Poste applies a specific pricing grid with weight tiers and size restrictions unique to each territory. A package compliant for mainland France may therefore be refused for an overseas destination.
Increased constraints for shipments to the United States
Since changes in U.S. customs regulations, shipments of goods to the United States are subject to stricter controls. For items weighing less than 2 kg and less than 3 cm thick, a goods mail offer remains possible. Beyond these thresholds, the shipment must switch to a package with complete customs formalities, including CN22 or CN23 declarations.
This thickness/weight distinction thus determines the applicable offer type even before considering the maximum dimensions of the Colissimo.
New taxes in 2026 on small imported packages outside the EU
The dimensions of a Colissimo not only affect shipping but also influence import taxation. As of March 1, 2026, a “Small Packages” tax of 2 euros per item applies to low-value goods from countries outside the European Union, destined for mainland France and certain DOM.
Starting July 1, 2026, the European Union will eliminate the duty-free allowance for shipments valued at 150 euros or less. A flat customs duty of 3 euros per item will now be added to each line of declaration for imports from outside the EU.
By combining these two levies, every small imported package incurs at least 5 euros in additional tax charges, regardless of its size. This change alters the economic balance between different shipping methods:
- The international tracked letter remains relevant for very compact and low-value items but no longer benefits from tax advantages
- The standard Colissimo offers tracking and compensation, justifying its overall cost once taxes are included
- For bulk shipments, consolidating multiple items into a single package reduces the number of declaration lines and thus the amount of flat duties
Choosing the package format thus takes on a new fiscal dimension. A more compact package does not reduce taxes, but grouping items in a single shipment can limit the multiplication of flat duties.
Before preparing a Colissimo in 2026, checking the dimensions remains the first reflex, but calculating the total cost must now include these customs levies. A package compliant with La Poste’s dimensions and properly declared in customs arrives at its destination without unexpected costs or returns to the depot.