What causes EFRIS error 15?

EFRIS error 15 is a data decryption error, and it almost never means your payload is malformed. It means URA could not decrypt the request because the AES session key you encrypted with is no longer the one the server holds — the key was negotiated by T104 and has since expired or been superseded server-side. The fix is to discard the cached key, perform a fresh T104 key exchange, and resend the same document. Retrying without renegotiating fails identically. If a second attempt still returns 15, suspect the certificate instead: it may not be the one URA holds for that TIN and device number.

How long does an EFRIS session key last?

URA does not publish a fixed lifetime. Clients typically cache the key from T104 for around 24 hours and renegotiate on expiry, but the server can invalidate a key earlier, which is exactly what produces error 15. Treat the validity window as a hint rather than a guarantee and always handle 15 by re-running T104 rather than by assuming the key is still good.

Error codes / 15

EFRIS error 15 — the session key expired server-side

Not a problem with your payload. URA expired the AES session key while your client still considered it valid, so the request could not be decrypted. Discard the cached key, redo the T104 handshake, and resend the same document once.

Retrying without renegotiating the key fails identically. The fix is to force a fresh T104, not to resend.

What it actually means

Session keys are negotiated by T104 and cached client-side for a validity window. URA can invalidate one earlier than the client expects — after a service restart, or when a newer session supersedes it. The client then encrypts with a key the server no longer holds, and every call fails with 15 until the key is replaced.

The fix

Clear the key and exchange a new one before resending. A single retry is enough; if the second attempt also returns 15, the cause is the certificate rather than the session.

from efris import EfrisError

try:
    client.upload_invoice(document)
except EfrisError as exc:
    if exc.code == "15":
        client.aes_key = None      # discard the stale session key
        client.exchange_key()      # fresh T104
        client.upload_invoice(document)
    else:
        raise

Why this happens

The library does this automatically on a first 15, so application code rarely needs the block above. It is shown because the same recovery is required in any implementation, and because a retry loop that does not renegotiate will spin forever.

Error 2253 — The seller's reference number has already been issued
Error 1526 — pageSize must be 99 or less, despite the documented 100
All EFRIS error codes

The EFRIS API Kit handles this case already — it is one of the rejections the library was calibrated against. This page stays free either way.

EFRIS error 15 — the session key expired server-side

What it actually means

The fix

Why this happens

Related