Identity, Tax & Invoice Processing (S5-S7)

§5 — Identity from the Secure Element

The taxpayer identity is read directly from the SE certificate — nothing is entered by the operator.

§6 — Tax calculation & rate management

Tax is calculated per item label against the active tax-rate group. Each tax category is applied by its type:

• Tax on net — added to the net amount.
• Tax on total — included within the price.
• Per-quantity — a fixed amount per unit.

Amounts are computed to 4 decimal places with half-round-up and presented to 2 decimals on the response and journal. Invoices carrying a label outside the active group are rejected at validation (§17).

Effective-dated groups

Tax-rate groups are installed by SetTaxRates (online) and can also be applied from the local-audit file. Future-dated groups take effect from their effective date; where dates coincide, the higher revision applies. The group in force at the invoice's referent date is used (current date for a normal sale; the original date for a copy/refund).

§7 — Invoice processing pipeline

1. Receive — an invoice request arrives on the POS-to-SDC service as JSON.
2. Validate — structure, labels and amounts are checked; invalid requests are rejected with the proper error code (§16).
3. Calculate — taxes are computed on the active rates for the referent date (§6).
4. Certificate check — a proactive validity check ensures the SE certificate is valid for the current date before signing.
5. Sign — the request, SDC date/time and cached PIN are sent to the SE, which returns the signature, encrypted internal data and counters (§2).
6. Journal — a 40-column textual receipt is produced with the verification URL and QR code (§8).
7. Store — the encrypted audit package is committed to non-volatile storage before the response is returned (§9).
8. Respond — the fiscal result is returned to the POS.

Auditing runs on a background service that does not hold the card lock, so a POS sign is never queued behind a network operation.