# Tax category

Classification of tax treatment (e.g., standard, exempt, zero-rated).

## Definition

Classification of tax treatment (e.g., standard, exempt, zero-rated).

## Why this term matters

Tax category drives the entire VAT calculation block (BT-118 per line, BG-23 per subtotal) and EN 16931 validators check arithmetic per category. Picking the wrong code (e.g., S Standard rate where AE Reverse charge applies) misstates the tax due, breaks BR-CO-* rules, and exposes the supplier to either over- or under-collection of VAT.

## Explanation

Often represented by standardized code lists in e-invoicing.

Used per line and/or per tax subtotal depending on syntax.

## Common mistakes

- Using "Z" (Zero rated) for exempt goods that should be "E" (Exempt) — they have different reporting consequences in most EU jurisdictions.
- Setting "AE" (Reverse charge) without populating BT-120 (VAT exemption reason) — BR-AE-10 fails.
- Mixing categories on a line that should be a single category, then having totals (BG-23) that disagree with the line sum.
- Hard-coding the German "K" (intra-Community supply) for cross-border invoices to non-EU countries — non-EU exports use "G".

## Frequently asked questions

### Which code list does EN 16931 use for tax category?
EN 16931 uses a restricted subset of UNTDID 5305: S (Standard rate), Z (Zero rated), E (Exempt from tax), AE (VAT reverse charge), K (VAT exempt for EEA intra-community supply), G (Free export item, VAT not charged), O (Services outside scope of tax), L (Canary Islands general indirect tax), and M (Tax for production, services and importation in Ceuta and Melilla).

### Do I need a tax category per line and per subtotal?
Yes. BT-151 sits on each invoice line, and BG-23 (VAT breakdown) groups all lines that share the same category and rate into a subtotal. The category on the line must match the category on the subtotal it rolls up to.

### When do I need BT-120 (exemption reason)?
For Z, E, AE, K, G, O, L, and M categories — anything that is not standard-rated. The reason text or code (BT-121) must explain why VAT is not charged so the recipient and tax authority can validate the treatment.

## Related resources

- [VAT category codes](/resources/code-lists/vat-category-codes)

## Related terms

- [Code list](/resources/glossary/code-list): A predefined set of allowed codes/values (e.g., VAT category, payment means).
- [Reverse charge](/resources/glossary/reverse-charge): VAT mechanism where the buyer accounts for VAT instead of the seller.