Issue Invoices with Line-Item Detail via WSMTXCA

WSMTXCA is ARCA’s alternative CAE service for electronic invoices. Unlike WSFE — which only carries fiscal header totals — WSMTXCA transmits the full breakdown of every line item with each voucher. Use it when you need ARCA to register individual products, services, quantities, and per-item VAT alongside the authorisation code. The facturas SDK covers WSMTXCA with exactly the same high-level methods as WSFE: issue(), issueCreditNote(), issueDebitNote(), preview(), previewCreditNote(), and previewDebitNote(). You never build SOAP arrays manually — the SDK handles both encodings.

Opt in per call

Pass { service: "wsmtxca" } as the second argument to any issuance or preview method. The SDK never switches services automatically — not after a rejection, not after a timeout, and not based on invoice content.

import { createArcaClient } from "facturas";

const arca = createArcaClient();

const result = await arca.issue(input, { service: "wsmtxca" });

Without a service option, or with { service: "wsfe" }, the call goes to WSFE. The TypeScript return type narrows to the chosen service: with { service: "wsmtxca" }, result.request and result.sent carry WSMTXCA-specific types without any casts.

The `details` array

Add a details array to your input to supply line-item breakdown. Each element represents one line on the invoice.

string

required

Human-readable description of the product or service.

number

required

Quantity of units.

number

required

ARCA unit-of-measure code (e.g. 7 for units).

string

required

Unit price as a decimal string in major currency units with up to six decimal places (e.g. "100.000000"). This is the only monetary field in the SDK that is not an integer number of centavos.

number

required

ARCA VAT condition code for this item (e.g. 5 for 21%).

number

VAT amount for this item in integer centavos. Required for Class A invoices.

number

required

Total line amount including VAT, in integer centavos.

number

Optional discount amount in integer centavos.

string

Optional product or service code.

string

Optional ARCA matrix code.

number

Optional matrix unit quantity.

unitPrice is the only monetary exception in the SDK. Every other amount — vatAmount, amount, discount, header totals — is an integer in centavos. unitPrice is a decimal string in major units (e.g. pesos) to preserve the vendor’s full price precision, which can have up to six decimal places.

Totals must reconcile

Item amount values include VAT. The sum of your details items must reconcile with the fiscal header totals you supply through the items or amounts fields — the same fields WSFE uses. The details array adds line-item detail to the voucher; it does not replace the fiscal breakdown.

Full example

import { createArcaClient } from "facturas";
import type { IssueInput } from "facturas";

const arca = createArcaClient();

const input = {
  issuer: "responsable_inscripto",
  salesPoint: 1,
  to: { condition: "responsable_inscripto", cuit: "20123456789" },
  // Fiscal header — same structure as WSFE.
  items: [{ net: 10_000, vat: 21 }],
  // Line-item detail for WSMTXCA.
  details: [
    {
      description: "Product",
      quantity: 1,
      unit: 7,
      unitPrice: "100.000000",  // Decimal string, major units (pesos).
      vatCondition: 5,           // VAT condition code for 21%.
      vatAmount: 2100,           // Integer centavos: ARS 21.00.
      amount: 12_100,            // Total including VAT, integer centavos.
    },
  ],
} satisfies IssueInput;

const result = await arca.issue(input, {
  service: "wsmtxca",
  idempotencyKey: "order:abc-123",
});

if (result.kind === "authorized") {
  console.log("CAE:", result.voucher.cae);
  console.log("Voucher number:", result.voucher.number);
}

Previewing a WSMTXCA request

Call preview() with { service: "wsmtxca" } to inspect the full WSMTXCA request the SDK would send, without reserving a voucher number or contacting ARCA:

const preview = arca.preview(input, { service: "wsmtxca" });

// Inspect the WSMTXCA-specific request structure.
const total = preview.request.comprobanteCAERequest.importeTotal;
console.log("Total:", total);

To capture the exact request that was sent on a successful authorization, pass include: { exactInput: true } to issue(). The result.sent field will contain the WSMTXCA request object.

FCE invoices

Electronic credit invoices (FCE) work the same way across both WSFE and WSMTXCA. Supply fce: { cbu, alias?, transfer?, reference? } on the invoice and fce: { annulment, reference? } on the credit note — the SDK translates the fields to the correct encoding for each service:

Field	WSFE encoding	WSMTXCA encoding
CBU / alias	Optional fields 2101 and 2102	Additional data 21 (combined `c1`/`c2`)
Annulment	Optional field 22	Additional data 22
Transfer	Optional field 27	Additional data 27

Do not duplicate these entries through optionalFields when you are already using the fce option — the SDK populates them automatically.

Idempotency and retries

WSMTXCA reservations are stored as v: 2 records in your store and always carry the provider name. A reservation written by a WSMTXCA call cannot be replayed through WSFE — this prevents a rollback to an older SDK version from silently re-sending an itemized invoice as a header-only WSFE voucher. On a retry, WSMTXCA evidence verification compares the full line-item detail, not just the header total. If the lookup returns incomplete evidence, the result is indeterminate and nothing is re-sent. For direct access to the lower-level client.wsmtxca methods — issue(), getLastAuthorizedVoucher(), getVoucher() — see the Exact Layer reference.

Get Started

Core Concepts

Guides

CLI

Reference

Issue Invoices with Line-Item Detail via WSMTXCA

Opt in per call

The `details` array

Totals must reconcile

Full example

Previewing a WSMTXCA request

FCE invoices

Idempotency and retries

​Opt in per call

​The details array

​Totals must reconcile

​Full example

​Previewing a WSMTXCA request

​FCE invoices

​Idempotency and retries

Opt in per call

The `details` array

Totals must reconcile

Full example

Previewing a WSMTXCA request

FCE invoices

Idempotency and retries