# contracts.change_quantity

## What it does

Record an evidenced absolute seat or quantity count under the right's declared proration and decrease rules. expectedQuantity must match the count in force.

An optional bill records the charge atomically at its invoicedAmount on the right's declared price basis (before reductions, and before tax for exclusive treatment), the vendor's for a received right or the business's own for a provided one; an amount other than the frozen proration flags attention.priceDiffers. bill.taxAmount states the invoice tax in minor units, including zero; supplier tax uses that figure, with tax_differs review attention when it differs from derivation.

A received exclusive-tax seat-change charge with positive supplier tax, a stated invoicedAmount and no stated tax raises tax_amount_unconfirmed when the amount matches predicted price plus tax within one minor unit, or when proration is stated without an independent prediction. It is recorded as entered; bill.usageReviewItems returns the frozen review item, including on duplicate replays.

## Before you send it

An authorized OAuth connection may call it, including a headless client. Effective membership, application grant and token permissions still apply. Describe `contracts.change_quantity` through `GET /v1/catalog/commands/{name}` before acting.

The envelope may reference a registered source document of kind `source_document`, `activity_statement`, `contract`; this is separate from any evidence required by the input.

## Inputs

Put these fields inside the envelope's `input` object. The outer envelope names the command, a stable `idempotency_key` and `effective_at`; [request and recovery rules](/docs/api/) explain those separately. Use exact minor-unit integer strings for monetary fields. Take existing IDs from prior reads or command results; choose a new identity only where the command asks for one.

Required means required within its containing object; an optional parent can be omitted.

| Field | Type | Required | Meaning and accepted values |
|---|---|---|---|
| `contractId` | string | Yes |  Minimum length: `1`. Example: `"ctr_example"`. |
| `activityKey` | string | Yes |  Minimum length: `1`. Example: `"seats"`. |
| `sourceFactId` | string | Yes |  Minimum length: `1`. Example: `"admin:seat-change"`. |
| `requestedAt` | string | Yes |  Format: date-time. Minimum length: `1`. Example: `"2026-10-20T00:00:00Z"`. |
| `expectedQuantity` | string | Yes |  Pattern: `"^(0\|[1-9][0-9]*)$"`. Example: `"5"`. |
| `quantity` | string | Yes |  Pattern: `"^(0\|[1-9][0-9]*)$"`. Example: `"7"`. |
| `evidence` | object | Yes |   |
| `evidence.service` | array | Yes |  Items: object. Minimum items: `1`. Maximum items: `20`. |
| `evidence.service[].kind` | string | Yes |  Choose `"tap_message"`, `"x402_receipt"`, `"chain_tx"`, `"signed_doc"`, `"stripe_object"`, `"other"`. Example: `"other"`. |
| `evidence.service[].ref` | string | Yes |  Minimum length: `1`. Example: `"admin-log"`. |
| `evidence.service[].signer` | string | No |  Minimum length: `1`. |
| `bill` | object | No |   |
| `bill.sourceFactId` | string | Yes |  Minimum length: `1`. |
| `bill.evidence` | array | Yes |  Items: object. Minimum items: `1`. Maximum items: `20`. |
| `bill.evidence[].kind` | string | Yes |  Choose `"tap_message"`, `"x402_receipt"`, `"chain_tx"`, `"signed_doc"`, `"stripe_object"`, `"other"`. |
| `bill.evidence[].ref` | string | Yes |  Minimum length: `1`. |
| `bill.evidence[].signer` | string | No |  Minimum length: `1`. |
| `bill.invoicedAmount` | string | Yes |  Pattern: `"^(0\|[1-9][0-9]*)$"`. |
| `bill.taxAmount` | string | No |  Pattern: `"^(0\|[1-9][0-9]*)$"`. |
| `bill.dueDate` | string | No |  Format: date. Minimum length: `1`. |

## After acceptance

When the command emits events, its documented effects and receipt are recorded in the command transaction. The response returns `commandId`, `replayed`, the command-specific `result` below and emitted `events` with their IDs and CIDs. A command is not automatically a cash movement or revenue recognition: use the behavior above to determine what this command records.

Inspect `result` and the affected records or reports before continuing. Save returned identifiers for later calls. Fetch `GET /v1/commands/{id}` with `commandId` to recover the accepted receipt; retry the same intent with the same idempotency key if the response was lost. Some commands can succeed with `events: []` and return a transient result and `commandId` without persisting a receipt. A lookup of that ID can return null; retain the returned result and verify the affected record. Retrying can re-evaluate the current state rather than replay a stored result. A domain `no_change` is a separate success outcome with no persisted receipt.

### Result fields

Required means required within its containing object; an optional parent can be omitted.

| Field | Type | Required | Meaning and accepted values |
|---|---|---|---|
| `changeId` | string | Yes |  Minimum length: `1`. |
| `adjustment` | object | No |   |
| `credit` | object | No |   |
| `bill` | object | No |   |


[All commands](/docs/command-reference/) · [Operation and errors](/docs/api-reference/operations/commands-execute/) · [Reusable schemas](/docs/api-reference/components/)

Keep credentials out of prompts; rehearse writes only in a disposable sandbox.

## Exact request schema


```json
{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "type": "object",
  "properties": {
    "name": {
      "const": "contracts.change_quantity"
    },
    "input": {
      "type": "object",
      "additionalProperties": false,
      "required": [
        "contractId",
        "activityKey",
        "sourceFactId",
        "requestedAt",
        "expectedQuantity",
        "quantity",
        "evidence"
      ],
      "properties": {
        "contractId": {
          "type": "string",
          "minLength": 1
        },
        "activityKey": {
          "type": "string",
          "minLength": 1
        },
        "sourceFactId": {
          "type": "string",
          "minLength": 1
        },
        "requestedAt": {
          "type": "string",
          "minLength": 1,
          "format": "date-time"
        },
        "expectedQuantity": {
          "type": "string",
          "pattern": "^(0|[1-9][0-9]*)$"
        },
        "quantity": {
          "type": "string",
          "pattern": "^(0|[1-9][0-9]*)$"
        },
        "evidence": {
          "type": "object",
          "additionalProperties": false,
          "properties": {
            "service": {
              "type": "array",
              "minItems": 1,
              "maxItems": 20,
              "items": {
                "type": "object",
                "additionalProperties": false,
                "properties": {
                  "kind": {
                    "enum": [
                      "tap_message",
                      "x402_receipt",
                      "chain_tx",
                      "signed_doc",
                      "stripe_object",
                      "other"
                    ]
                  },
                  "ref": {
                    "type": "string",
                    "minLength": 1
                  },
                  "signer": {
                    "type": "string",
                    "minLength": 1
                  }
                },
                "required": [
                  "kind",
                  "ref"
                ]
              }
            }
          },
          "required": [
            "service"
          ]
        },
        "bill": {
          "type": "object",
          "additionalProperties": false,
          "properties": {
            "sourceFactId": {
              "type": "string",
              "minLength": 1
            },
            "evidence": {
              "type": "array",
              "minItems": 1,
              "maxItems": 20,
              "items": {
                "type": "object",
                "additionalProperties": false,
                "properties": {
                  "kind": {
                    "enum": [
                      "tap_message",
                      "x402_receipt",
                      "chain_tx",
                      "signed_doc",
                      "stripe_object",
                      "other"
                    ]
                  },
                  "ref": {
                    "type": "string",
                    "minLength": 1
                  },
                  "signer": {
                    "type": "string",
                    "minLength": 1
                  }
                },
                "required": [
                  "kind",
                  "ref"
                ]
              }
            },
            "invoicedAmount": {
              "type": "string",
              "pattern": "^(0|[1-9][0-9]*)$"
            },
            "taxAmount": {
              "type": "string",
              "pattern": "^(0|[1-9][0-9]*)$"
            },
            "dueDate": {
              "type": "string",
              "minLength": 1,
              "format": "date"
            }
          },
          "required": [
            "sourceFactId",
            "evidence",
            "invoicedAmount"
          ]
        }
      }
    },
    "idempotency_key": {
      "type": "string",
      "minLength": 1,
      "maxLength": 256
    },
    "effective_at": {
      "type": "string",
      "format": "date-time",
      "pattern": "^(?:(?:\\d\\d[2468][048]|\\d\\d[13579][26]|\\d\\d0[48]|[02468][048]00|[13579][26]00)-02-29|\\d{4}-(?:(?:0[13578]|1[02])-(?:0[1-9]|[12]\\d|3[01])|(?:0[469]|11)-(?:0[1-9]|[12]\\d|30)|(?:02)-(?:0[1-9]|1\\d|2[0-8])))T(?:(?:[01]\\d|2[0-3]):[0-5]\\d:[0-5]\\d(?:\\.\\d+)?(?:Z))$"
    },
    "source_document_id": {
      "description": "A registered document of kind source_document, activity_statement, contract that caused this command.",
      "type": "string",
      "minLength": 1
    }
  },
  "required": [
    "name",
    "input",
    "idempotency_key",
    "effective_at"
  ],
  "additionalProperties": false
}
```

## Accepted command receipt


```json
{
  "type": "object",
  "required": [
    "commandId",
    "replayed",
    "result",
    "events"
  ],
  "properties": {
    "commandId": {
      "type": "string"
    },
    "replayed": {
      "type": "boolean"
    },
    "imported": {
      "const": true,
      "description": "The command's events are history from before the business joined Economico, recorded as an import: free of monthly events."
    },
    "result": {
      "type": "object",
      "properties": {
        "changeId": {
          "type": "string",
          "minLength": 1
        },
        "adjustment": {
          "type": "object"
        },
        "credit": {
          "type": "object"
        },
        "bill": {
          "type": "object"
        }
      },
      "required": [
        "changeId"
      ]
    },
    "events": {
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "id": {
            "type": "integer"
          },
          "cid": {
            "type": "string"
          }
        }
      }
    }
  }
}
```

## Example request


```json
{
  "name": "contracts.change_quantity",
  "input": {
    "contractId": "ctr_example",
    "activityKey": "seats",
    "sourceFactId": "admin:seat-change",
    "requestedAt": "2026-10-20T00:00:00Z",
    "expectedQuantity": "5",
    "quantity": "7",
    "evidence": {
      "service": [
        {
          "kind": "other",
          "ref": "admin-log"
        }
      ]
    }
  },
  "effective_at": "2026-09-01T00:00:00Z",
  "idempotency_key": "contracts.change_quantity-example-0"
}
```