> ## Documentation Index
> Fetch the complete documentation index at: https://facturas-sdk.dev/llms.txt
> Use this file to discover all available pages before exploring further.
# Issue Invoices with Line-Item Detail via WSMTXCA
> Use { service: 'wsmtxca' } to send full line-item detail to ARCA's WSMTXCA service. Learn item fields, monetary precision, and how totals must reconcile.
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.
```typescript theme={null}
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.
Human-readable description of the product or service.
Quantity of units.
ARCA unit-of-measure code (e.g. `7` for units).
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.
ARCA VAT condition code for this item (e.g. `5` for 21%).
VAT amount for this item in integer centavos. Required for Class A invoices.
Total line amount **including VAT**, in integer centavos.
Optional discount amount in integer centavos.
Optional product or service code.
Optional ARCA matrix code.
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
```typescript theme={null}
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:
```typescript theme={null}
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/exact-layer) reference.