# SDI-00400

Source: https://xmlvalid.com/rules/SDI-00400

> 2.2.1.14 <Natura> non presente a fronte di 2.2.1.12 <AliquotaIVA> pari a zero

- Level: error
- Rule sets: SdI checks (FatturaPA ordinary invoice) Specifiche tecniche 1.9.1
- Context: `/p:FatturaElettronica/FatturaElettronicaBody/DatiBeniServizi/DettaglioLinee`
- Test: `$rate != 0 or Natura`

> 2.2.4 <Natura> non presente a fronte di 2.2.3.2 <Aliquota> pari a zero

- Level: error
- Rule sets: SdI checks (FatturaPA simplified invoice) Specifiche tecniche 1.9.1
- Context: `/s:FatturaElettronicaSemplificata/FatturaElettronicaBody/DatiBeniServizi`
- Test: `not($rate) or it:dec($rate) != 0 or Natura`

In English: Natura is missing on a line (2.2.1.14) whose VAT rate (2.2.1.12) is zero; in a simplified invoice, Natura (2.2.4) with a zero Aliquota (2.2.3.2).

## Why it fails

- A line without VAT (exempt, non-taxable, out of scope, reverse charge) has `AliquotaIVA` 0.00 but no `Natura` saying why.

## How to fix it

- Add `Natura` after `AliquotaIVA` on that line with the detailed code that applies (N1, N2.1, N2.2, N3.1 to N3.6, N4, N5, N6.1 to N6.9, N7), and the same code in the matching `DatiRiepilogo`.

Validate a document against these rules: https://xmlvalid.com/validate