Developers

API reference

A predictable REST API: plural resources, JSON in and out, amounts in the currency's smallest unit and explicit errors.

Reference still being aligned with the implementation: confirm every signature with the technical team before relying on it in production. Remove this notice once the documentation is approved.

Base URL

All requests go over HTTPS to this base. Plain HTTP calls are rejected.

https://api.nexet.io/v1

The version is part of the path. A new major version is only released for a breaking change; new fields are added without changing the version.

Authentication

Authentication uses your secret key with HTTP basic auth: the key is the username, the password stays empty.

curl https://api.nexet.io/v1/payments \
  -u sk_test_4dLm…:

Each environment has its own key pair: sk_test_… in the sandbox, sk_live_… in production.
The secret key must never be exposed in the browser or committed to a repository. It can be revoked and rotated from the merchant space with no downtime.

Idempotency

Every creation endpoint accepts an Idempotency-Key header. Replaying the same key returns the original response instead of creating a second object: no double payment on a network retry.

-H "Idempotency-Key: ord-1042"

Errors

Errors use standard HTTP codes and return an error object describing the cause. Pass the request identifier on to support.

{
  "error": {
    "type": "card_declined",
    "code": "insufficient_funds",
    "message": "The card has insufficient funds.",
    "request_id": "req_8Kd92mLp"
  }
}

Code	type	Meaning
400	invalid_request	Missing or invalid parameter.
401	authentication_error	API key missing, invalid or revoked.
402	card_declined	Payment declined by the card issuer.
404	not_found	The requested resource does not exist.
409	idempotency_conflict	Idempotency key reused with a different body.
429	rate_limit	Too many requests: retry with increasing backoff.
500	api_error	Incident on the Nexet Pay side. The request can be replayed.

Pagination

Lists are cursor-paginated: limit sets the page size, starting_after resumes after the given identifier. The response indicates whether more items remain.

GET /v1/payments?limit=50&starting_after=pay_3jF8dK2m

Payments

Collect, retrieve, capture and refund a payment.

POST	/v1/payments	Create a payment (immediate capture or authorisation).
GET	/v1/payments/{id}	Retrieve a payment and its status.
GET	/v1/payments	List payments, with status and date filters.
POST	/v1/payments/{id}/capture	Capture all or part of an authorisation.
POST	/v1/payments/{id}/refunds	Refund a payment, in full or in part.

Payment links

Create shareable payment links, with a fixed or open amount.

POST	/v1/payment_links	Create a payment link and its QR code.
GET	/v1/payment_links/{id}	Retrieve a link and its payment counter.
GET	/v1/payment_links	List payment links.
POST	/v1/payment_links/{id}/deactivate	Deactivate a link before its expiry date.

Subscriptions

Define plans and manage the subscription lifecycle.

POST	/v1/plans	Create a subscription plan (amount, frequency, trial).
POST	/v1/subscriptions	Subscribe a customer to a plan.
GET	/v1/subscriptions/{id}	Retrieve a subscription and its current cycle.
POST	/v1/subscriptions/{id}/cancel	Cancel a subscription, immediately or at period end.

Invoices

Issue invoices and track their payment.

POST	/v1/invoices	Create an invoice with its line items and VAT.
POST	/v1/invoices/{id}/send	Email the invoice with its payment button.
GET	/v1/invoices/{id}	Retrieve an invoice and its payment status.
GET	/v1/invoices	List invoices.

Customers

Store your customers and their tokenised payment methods.

POST	/v1/customers	Create a customer and store their payment methods.
GET	/v1/customers/{id}	Retrieve a customer.
GET	/v1/customers	List customers.

Webhooks

Declare an endpoint URL from your merchant space: every event is POSTed there, with exponential retries until acknowledged (2xx response).

Each request carries a Nexet-Signature header with the timestamp and an HMAC signature of the body. Verify it before processing the event, and reject timestamps that are too old.

Nexet-Signature: t=1786982400,v1=5f2c…

Events emitted

payment.succeededpayment.failedpayment.refundeddispute.openedsubscription.renewedsubscription.canceledinvoice.paidinvoice.payment_failedpayout.paid

Test environment

The sandbox is free and unlimited. Simulation cards let you trigger each scenario with no real movement of funds.

Scenario	Expected result
Payment accepted	succeeded status, simulated settlement.
3-D Secure authentication required	requires_action status, then 3DS redirect.
Card declined	card_declined error with the decline reason.

The full list of test cards and their decline codes is available in your merchant space, under Test environment.

A question about your integration?

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