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Cart mandates explained for merchants
A cart mandate is a record of what a shopper authorised an agent to buy: the items, the quantities and the amount. It exists so a purchase can be checked against the permission that produced it, and its practical consequence for a merchant is that pricing accuracy stops being a presentation question and becomes a settlement one.
Why the concept is needed
When a person clicks buy, the authorisation and the purchase are the same act. When an agent buys on somebody’s behalf, they are separated in time, and something has to connect them. Without that link, "the agent bought something I did not agree to" has no resolution.
What it changes for a merchant
It makes your published price load bearing in a new way. If your listed price and your charged price differ, that is no longer a presentation inconsistency, it is a mismatch between a purchase and the authorisation for it.
The common causes are ordinary: a discount applied at render but not in structured data, a stale feed carrying an old price, a shipping cost that appears only at checkout. Each becomes more consequential here. See how to keep a product feed fresh.
The practical implications
- Publish the price a shopper actually pays, in every place you publish a price.
- Rebuild your feed on price change rather than on a schedule.
- Make the delivered total computable before checkout, so the authorised amount is the real amount.
- Keep availability accurate, so a mandate is not issued for something you cannot supply.
Where it sits
Mandates are produced and checked at the payment and platform layer rather than by individual stores, so for most merchants this is context rather than a task. See the Agent Payments Protocol for merchants.
Questions
What happens if my price changed between the mandate and the purchase?
That is exactly the case mandates make visible, and the handling depends on your platform and provider. It is a strong argument for a feed that rebuilds on price change rather than nightly.
Do I need to store mandates myself?
On a hosted platform, generally not: they are handled at the layer that processes the payment. Knowing they exist matters more than holding them, because it explains why your published price is now load bearing.
Does this make disputes easier or harder?
In principle easier, since there is a record of what was authorised. In practice it depends on your provider and jurisdiction, which is worth asking about directly.