Hungary — NAV Sandbox Onboarding

Operational guide for getting test credentials at the Hungarian NAV Online Számla sandbox.

Property	Value
Authority	NAV (Nemzeti Adó- és Vámhivatal)
Sandbox base URL	`https://api-test.onlineszamla.nav.gov.hu/invoiceService/v3`
API version	3.0
Cost	Free
Time to provision	1-3 days
Identity required	Hungarian tax number (real or NAV-issued test taxpayer)

Steps

Register or log into the NAV Online Számla developer portal at onlineszamla.nav.gov.hu.
Inside your taxpayer profile, create a technical user (műszaki felhasználó) — this is a separate account from the human login.
NAV generates four credentials:
- password — hash with SHA-512 before sending in requests
- signatureKey — used for SHA3-512 request-signing
- exchangeKey — used to decrypt the AES-128/ECB-encoded session token
- The technical user's login (handle)
Note your taxNumber (8 digits + VAT code + county code) and softwareId (assigned per integration, not per merchant).
Validate by issuing tokenExchangeRequest against the sandbox.

HU_NAV_TAX_NUMBER
HU_NAV_TECH_USER_LOGIN
HU_NAV_TECH_USER_PASSWORD
HU_NAV_SIGNATURE_KEY
HU_NAV_EXCHANGE_KEY
HU_NAV_SOFTWARE_ID

softwareId is per-integration, not per-merchant. One value covers all your test taxpayers.
Sandbox uses API v3.0 — no FA(2)/FA(3) migration drama (that's a Polish concern).
Request signature must implement BOTH SHA-512 and SHA3-512. SHA-512 is for password hashing, SHA3-512 is for the per-request signature. Adapter at rust/adapters/hungary/src/auth.rs already does this.
The 4-second request signature window is enforced strictly — clock skew is the most common authentication failure in sandbox testing. Use NTP-synced clock.

The software-vendor track is openly accessible. NAV's developer portal accepts foreign software vendors with no Hungarian residency requirement.

No local entity required for sandbox. Register as a foreign software vendor at onlineszamla.nav.gov.hu; test taxpayer numbers can be requested without holding a Hungarian taxpayer of your own.
softwareId is per-integration, not per-merchant — one value covers all your test taxpayers, and we issue it once for the whole platform regardless of where Zyntem is incorporated.
Production constraint. NAV reports merchants' domestic sales; the merchant must be a Hungarian VAT subject. The software platform does not need to be a HU entity — we onboard Hungarian merchants directly and they sit on their own taxpayer record.
Cheapest path: apply directly via the NAV developer portal. ~1 week. No fiscal representative needed.