A charge is an invoice on a contract. A contract may have one or many charges depending on how it was created.

How Charges Are Created

One-time payments: a single charge is created
Recurring (frequency-based) contracts: a new charge is generated each billing cycle (e.g., monthly) as the cycle becomes due
Scheduled-charges contracts: the full set of charges is created upfront from the explicit charges[] array supplied at contract creation. Each charge carries its own amount, due date, and optional alt_key

Each charge tracks:

The amount due
When it's due
How much has been paid
How much is outstanding
Whether it's been written off

For recurring and one-time contracts you don't create charges manually — they are generated automatically. For scheduled-charges contracts, all charges are materialised at the moment the contract is created. In both cases, to retrieve the charges on a contract use List contract charges.

Status Flow

Status	Description
`ACTIVE`	The charge has been raised but not yet fully paid
`PENDING`	The charge has been paid but the transaction is still pending confirmation
`COMPLETED`	The charge has been fully paid
`WRITTENOFF`	The charge has been fully or partially written off

Modifying Charges

You can update a charge to:

Write off an outstanding balance by setting status to WRITTENOFF
Change the amount due (cannot be less than the amount already paid)
Change the due date: note that setting a past due date may trigger an immediate payment attempt