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. 
 
 Field Source in the certificate 
 
 TIN Certificate OID (tag-6) 
 UID SERIALNUMBER (subject) 
 Company name Subject O 
 Store / business unit Subject OU 
 Address Subject STREET 
 District Subject S 
 TaxCore endpoint Certificate extension (tag-5) — the environment URL 
 
 

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