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The e-Invoice and E-Way Bill APIs support NIC1 and NIC2. Two optional headers control which session and server a request uses.

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x-source

x-source selects the NIC server when you authenticate. On later requests, it selects that server’s stored session. If omitted, x-source defaults to primary on each request. Authenticating with NIC2 does not change this default. A request with x-source: secondary needs an existing NIC2 session for the same workspace and GSTIN. Changing the header does not create a session.

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x-proxy

x-proxy sends the request to the other NIC server with the session selected by x-source. If omitted, the request goes to the server selected by x-source. It accepts primary or secondary and must differ from x-source. An invalid or matching value returns HTTP 422 with Invalid x-proxy.

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Examples

Each example requires the session shown below for the same workspace and GSTIN.