mcp-invoicenow-sg 🇸🇬

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Introduction

mcp-invoicenow-sg is an MCP (Model Context Protocol) server for Singapore electronic invoicing over InvoiceNow, the national e-invoicing platform operated by IMDA. It builds and validates PINT-SG v1.4.1 and SG Peppol BIS Billing 3.0 sent invoices (originally-issued invoices, not the received/purchase side). It is part of the mcp-einvoicing-* family of country-specific servers, all built on mcp-einvoicing-core, which provides the shared validation engine, EN 16931 abstractions, and Peppol network utilities.

Supported standards

• PINT-SG v1.4.1 (urn:peppol:pint:billing-1@sg-1) — the recommended profile for new senders.
• SG Peppol BIS Billing 3.0 — legacy profile, predates the PINT programme.
• Both are EN 16931-conformant; the invoice model extends mcp_einvoicing_core.en16931.EN16931Invoice.
• Validation runs IRAS's own C5 acceptance layer (non_peppol_doc_validation) — a first-party government artifact, e.g. it flags a missing buyer/seller UEN. As of v0.2.0, PINT-SG's own jurisdiction Schematron rules (e.g. the invoice_uuid requirement) are not checked — see "Not yet supported" below.

Not yet supported (see specs/README.md for full detail):

• CEN EN16931 base and PINT-SG jurisdiction Schematron validation. v0.1.0 bundled a self-compiled derivative of OpenPeppol's PINT-SG jurisdiction Schematron with no confirmed redistribution rights; it was removed in v0.2.0 (2026-08-28). The shared, properly-licensed core CEN EN16931 base validator is wired but not yet activated for SG — SGInvoice's IRAS GST category codes have no sourced crosswalk to the UNCL5305 code list that validator requires. See EN16931_BASE_UNAVAILABLE_WARNING in every validate_invoice_sg result (tracked as [CORE-EN16931-BASE-SG-CROSSWALK-1]) for what would unblock it.
• The Peppol Ordering message family (Order, OrderResponse, etc.) and IMDA's SG-specific Order Balance.
• UBL 2.1 XSD structural validation. Proven correct against a real UBL 2.1 schema in this package's own test suite (a test-only fixture, not shipped in the wheel), but not wired into the validate_invoice_sg tool: the OASIS UBL 2.1 schema files needed carry no locally-confirmed redistribution grant.
• IRAS's own Invoice Data Submission API (the 5th-corner "C5" copy specifically, as distinct from generic Peppol AS4 transport, which the Peppol tools below do support) — no publicly available document states an IMDA-accredited Access Point's actual API base URL or authentication flow.
• SG Peppol BIS Billing 3.0 Schematron validation — no rule set is bundled for this profile.
• The received/purchase-side invoice model (LocalTaxInvoice, TX2_Annex Annex B Type 1B).

Installation

Requirements

• Python ≥ 3.11
• mcp-einvoicing-core (installed automatically as a dependency)
• Optional: the xslt2 extra (pip install mcp-invoicenow-sg[xslt2]) — required for validate_invoice_sg to run. The bundled IRAS C5 stylesheet requires XSLT 2.0.

Using uvx (recommended)

uvx mcp-invoicenow-sg

Using uv

uv add mcp-invoicenow-sg

From source

git clone https://github.com/cmendezs/mcp-invoicenow-sg.git
cd mcp-invoicenow-sg
uv sync --all-extras

Configuration

Environment variables

This server needs no credentials to run.

Claude Desktop integration

To use this server with Claude, add this configuration to your claude_desktop_config.json file:

{
  "mcpServers": {
    "invoicenow-sg": {
      "command": "uvx",
      "args": ["mcp-invoicenow-sg"]
    }
  }
}

Cursor integration

Cursor supports MCP servers via stdio. Add the configuration in:

• Global (all projects): ~/.cursor/mcp.json
• Project (this repository only): .cursor/mcp.json

{
  "mcpServers": {
    "invoicenow-sg": {
      "command": "uvx",
      "args": ["mcp-invoicenow-sg"]
    }
  }
}

Reload the Cursor window (Ctrl+Shift+P then Reload Window) to apply the changes.

Kiro integration

Kiro supports MCP servers via its dedicated configuration file. Two levels are available:

• Global (all projects): ~/.kiro/settings/mcp.json
• Workspace (this repository only): .kiro/settings/mcp.json

{
  "mcpServers": {
    "invoicenow-sg": {
      "command": "uvx",
      "args": ["mcp-invoicenow-sg"],
      "disabled": false,
      "autoApprove": []
    }
  }
}

The file is automatically reloaded on save. You can also open the config via the command palette (Cmd+Shift+P / Ctrl+Shift+P) then MCP.

Available tools

Recommended workflow: get_profile_urn_sg to pick the profile pair, then generate_invoice_sg with that pair in the invoice data, then validate_invoice_sg on the result.

Peppol tools

Generic Peppol network tools (participant lookup, AS4 send, directory search, eDEC codelists) are also registered, from mcp_einvoicing_core.peppol.tools, with bare Singapore UENs normalized to scheme 0195 participant IDs:

peppol_send is generic Peppol AS4 transport to the recipient's Access Point — it is not the same as submission to IRAS's own C5 corner, which stays unsupported (see "Not yet supported" above).

The tool reference in docs/TOOLS.md is generated from the running server:

uv run python scripts/gen_tool_reference.py

Vendor neutrality

This server implements the standard itself: it builds, validates, and signs the document locally. It is not a client for a commercial invoicing platform, and your signing keys and credentials never leave your own infrastructure.

A Peppol access point is required for InvoiceNow, but any accredited access point speaks the same AS4 profile, so switching providers is a configuration change, not a code change.

Contributing

See CONTRIBUTING.md for development setup, the test and lint commands, and the pull request checklist. Security issues follow the private disclosure process in SECURITY.md.

Other e-invoicing MCP servers

License

This project is licensed under the Apache 2.0 license — see LICENSE for details. For the full version history, see CHANGELOG.md.