---
title: "Signing In to a Merchant Account"
method: POST
path: "/v1/auth/external/sign-in"
tags: ["JWT Authentications"]
---

# Signing In to a Merchant Account

`POST /v1/auth/external/sign-in`

Sign in to an existing Helio merchant account using an external authentication method.

## Query parameters

- `apiKey` string, required

## Request body

- SessionUpdateRequest
  - `id` string, required — The merchant-generated unique identifier used as a stable external reference for the account.

## Response `200`

Returns user and company details along with a redirect URL.

- PaylinkTxWithShallowEnrichedPaylink

## Other responses

- `401` — Provided API key has no access to the resource.

---

[API](https://skmtc.net/hel/apis/helio-open-api.md) · [All operations](https://skmtc.net/hel/apis/helio-open-api/llms.txt) · [OpenAPI document](https://skmtc-service-staging.skmtc.workers.dev/v1/apis/hel/helio-open-api/revisions/5732beb2d39f/schema)