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Most products are fixed - they have a single price. Open-denomination products let you choose any amount within an allowed range (for example, a top-up between £5 and £100).

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Identifying open products

Each catalog product includes denomination metadata:
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denominationType
string
fixed or open.
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denominationMinValue
number
Minimum amount (minor units) for open products.
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denominationMaxValue
number
Maximum amount (minor units) for open products.
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denominationStep
number
Increment the chosen amount must align to.
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denominationDefaultValue
number
Suggested default amount.

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Ordering an open product

Send your chosen amount as the line price. It must fall within [min, max] and align to step.
Amounts outside the allowed range are rejected with 400 Bad Request. For fixed products, the line price must exactly match the catalog price.