> ## Documentation Index > Fetch the complete documentation index at: https://docs.fastcac.com/llms.txt > Use this file to discover all available pages before exploring further. # Monitor a business > Watches a business on CAC's register. It's read once a day, and a change in its status or name sends `business.status_changed` or `business.name_changed` to your webhook endpoints. Charged from your wallet for 30 days at a time (see `amount_charged`); each renewal is charged when `paid_through` passes, and a renewal your wallet can't cover pauses the monitor (`monitor.paused`) until it can. Test monitors are never read from CAC: change one with the test helper. ## OpenAPI ````yaml /openapi.json post /businesses/monitors openapi: 3.1.0 info: title: FastCAC API description: Register Nigerian businesses with CAC from your own product. version: '2026-11-01' servers: - url: https://api.fastcac.com/v1 security: - apiKey: [] tags: - name: Account description: Check your key and see your organization. - name: Names description: >- Check a business name against CAC's rules and registry, and the categories it takes, before registering it. - name: Registrations description: Register a Business Name with CAC, from draft to certificate. - name: Lookup description: >- Search CAC's register for free, and look up a business's full record with its officers. - name: Verification description: >- Check that a business your applicant names is real, active and run by the people they say. - name: Monitoring description: >- Watch businesses on CAC's register and get an event when one goes inactive or changes name. - name: Identities description: >- Look up a proprietor's NIN with NIMC, to prefill a registration and use their photo. - name: Balance description: >- Your prepaid wallet: what's available, its transactions and your funding account. - name: Test helpers description: >- Test keys only: move a registration on without waiting, or simulate a deposit. - name: Webhooks description: Endpoints that receive events, and the events sent to them. - name: Webhook events description: What FastCAC POSTs to your webhook endpoints. paths: /businesses/monitors: post: tags: - Monitoring summary: Monitor a business description: >- Watches a business on CAC's register. It's read once a day, and a change in its status or name sends `business.status_changed` or `business.name_changed` to your webhook endpoints. Charged from your wallet for 30 days at a time (see `amount_charged`); each renewal is charged when `paid_through` passes, and a renewal your wallet can't cover pauses the monitor (`monitor.paused`) until it can. Test monitors are never read from CAC: change one with the test helper. operationId: create_monitor_businesses_monitors_post parameters: - name: simulate in: query required: false schema: anyOf: - type: string - type: 'null' description: >- Test keys only: cac_record_missing (404) or insufficient_balance (402). Ignored with a live key. title: Simulate description: >- Test keys only: cac_record_missing (404) or insufficient_balance (402). Ignored with a live key. requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/MonitorIn' example: number: RC 7654321 external_id: merchant-4471 responses: '201': description: Successful Response content: application/json: schema: $ref: '#/components/schemas/V1BusinessMonitor' examples: Example: value: object: business_monitor id: mon_5Rfxqm9UQ4xlFxXoJeFCaT number: '7654321' type: RC type_label: Company name: ADA FOODS LIMITED status: ACTIVE active: true external_id: merchant-4471 state: active paid_through: '2026-11-27T15:16:04Z' last_checked_at: null last_changed_at: null amount_charged: '100.00' created_at: '2026-10-28T15:16:04Z' '400': description: The request is invalid; `param` names the field. content: application/json: schema: $ref: '#/components/schemas/Error' '401': description: The API key is missing, malformed, revoked or expired. content: application/json: schema: $ref: '#/components/schemas/Error' examples: Example: value: error: type: authentication_error code: api_key_missing message: 'Send your API key as `Authorization: Bearer `.' param: null request_id: req_8r9FEwNmLuxQORZX5Qhvkd0q '402': description: >- The wallet can't cover 30 days: `insufficient_balance`. Nothing was charged. content: application/json: schema: $ref: '#/components/schemas/V1Error' examples: Example: value: error: type: payment_error code: insufficient_balance message: >- Your balance is ₦0.00; monitoring a business costs ₦100.00 for 30 days. Fund your wallet by bank transfer to your funding account, then try again. param: null request_id: req_GV3JxZlBlquNBBSjEqFGHnag details: amount_due: '100.00' balance: '0.00' currency: NGN funding_account: account_number: '0000000000' bank_name: TEST BANK account_name: FastCAC - TEST MODE '403': description: >- The key can't do this (for example, a test helper called with a live key). content: application/json: schema: $ref: '#/components/schemas/Error' examples: Example: value: error: type: permission_error code: live_mode_unavailable message: >- Live registrations are paused right now. Use a test key (fc_test_…) meanwhile. param: null request_id: req_Td9lI1vsT5ARzv0XD7RGS1tD '404': description: >- `cac_record_missing`: CAC has no business with that number. Not charged. content: application/json: schema: $ref: '#/components/schemas/V1Error' examples: Example: value: error: type: not_found_error code: cac_record_missing message: >- CAC has no business with that number. You weren't charged. param: number request_id: req_Y68cfGTTJjBHCCRQaS2tDHhh '409': description: >- `monitor_exists`: you already monitor it; `details.monitor` is its id. content: application/json: schema: $ref: '#/components/schemas/V1Error' examples: Example: value: error: type: invalid_request_error code: monitor_exists message: You already monitor RC 7654321. param: number request_id: req_pih9euyk6J6Ge0u2TkjaNeO8 details: monitor: mon_5Rfxqm9UQ4xlFxXoJeFCaT '429': description: Too many requests; wait for `Retry-After` seconds. content: application/json: schema: $ref: '#/components/schemas/Error' components: schemas: MonitorIn: properties: number: type: string title: Number description: >- The registration number, with or without its prefix: "8911267" or "RC 8911267". type: anyOf: - type: string enum: - BN - RC - IT - LP - LLP - type: 'null' title: Type description: >- The register. Needed only when the number is in more than one (`type_required`). external_id: anyOf: - type: string maxLength: 255 - type: 'null' title: External Id description: Your own reference, sent back in every event. type: object required: - number title: MonitorIn V1BusinessMonitor: properties: object: type: string const: business_monitor title: Object default: business_monitor id: type: string title: Id description: mon_… number: type: string title: Number type: type: string enum: - BN - RC - IT - LP - LLP title: Type type_label: type: string title: Type Label name: type: string title: Name description: The registered name at the last check. status: type: string title: Status description: >- CAC's status at the last check: ACTIVE, INACTIVE, STRUCK OFF and so on. active: type: boolean title: Active description: True when `status` is ACTIVE. external_id: anyOf: - type: string - type: 'null' title: External Id state: type: string enum: - active - paused - deleted title: State description: >- paused: a 30-day renewal couldn't be charged; it resumes once your wallet can pay. deleted: you stopped it. paid_through: type: string title: Paid Through description: When the current 30 days end; it renews then. last_checked_at: anyOf: - type: string - type: 'null' title: Last Checked At description: The last time CAC's register was read for it. last_changed_at: anyOf: - type: string - type: 'null' title: Last Changed At description: The last time its name or status changed. amount_charged: anyOf: - type: string - type: 'null' title: Amount Charged description: 'On create only: what the first 30 days cost.' created_at: anyOf: - type: string - type: 'null' title: Created At type: object required: - id - number - type - type_label - name - status - active - external_id - state - paid_through - last_checked_at - last_changed_at - created_at title: V1BusinessMonitor Error: properties: error: $ref: '#/components/schemas/ErrorDetail' required: - error title: V1Error type: object V1Error: properties: error: $ref: '#/components/schemas/ErrorDetail' required: - error title: V1Error type: object ErrorDetail: properties: type: type: string enum: - invalid_request_error - authentication_error - payment_error - permission_error - not_found_error - idempotency_error - rate_limit_error - api_error title: Type code: type: string title: Code description: Stable and machine-readable, e.g. registration_incomplete. message: type: string title: Message description: For a developer to read; may change. param: anyOf: - type: string - type: 'null' title: Param description: The parameter at fault, as a path like proprietors[0].nin. request_id: anyOf: - type: string - type: 'null' title: Request Id description: Also in the FastCAC-Request-Id header. Quote it to support. details: anyOf: - additionalProperties: true type: object - type: 'null' title: Details description: >- Only on some errors. A 402 insufficient_balance carries amount_due, balance, currency and funding_account (number, bank, name; null until it's active). type: object required: - type - code - message - param - request_id title: ErrorDetail securitySchemes: apiKey: type: http scheme: bearer description: 'Your secret API key: fc_test_… in test mode, fc_live_… in live mode.' ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.