Customer group mapping

The module assigns customers to one of three configurable groups based on the validation outcome. It does not create the groups or the tax rules — that's standard Magento territory.

The chain

Validation result
    ↓
Module assigns customer group
    ↓
Customer group's tax class
    ↓
Tax rule mapping (customer tax class + product tax class + country)
    ↓
Tax rate

Every link must be intact. Native Magento falls back to default behaviour when any link breaks — and that's almost always why "VIES says valid but they're still being charged 19%" support tickets happen.

The three buckets

Setting	Applied when	Typical use
Group for Domestic Valid	Buyer country == requester country	Still pays domestic VAT
Group for Intra-EU / UK Valid (Zero Tax)	Buyer country != requester country	Reverse charge / 0%
Group for Invalid	Upstream returned invalid	Fall back to consumer pricing

When VIES / HMRC / UID-CHE returns unavailable (timeout, 5xx, malformed response) the customer's current group is preserved — we never downgrade based on a flaky upstream.

Worked example: German store, French B2B buyer

Goal: French B2B buyer with valid VAT pays 0% (intra-EU reverse charge).

1. Stores → Customer Groups — create "B2B EU Valid", tax class "Reverse Charge B2B"
2. Stores → Tax Zones and Rates — create rate EU Reverse Charge = 0%, country = "All countries"
3. Stores → Tax Rules — create rule:
   • Customer Tax Class: Reverse Charge B2B
   • Product Tax Class: Taxable Goods (whatever your products use)
   • Tax Rate: EU Reverse Charge
4. Module config → Customer Group Mapping → "Group for Intra-EU / UK Valid VAT (Zero Tax)" = B2B EU Valid

Place a test order from a French B2B account with a valid French VAT. The tax line should be 0.

Disabling auto-assignment

If your ERP owns customer-group assignment and you only want validation + audit logging, set Auto-Assign Customer Group = No. The module will continue validating and persisting to the log, but won't touch customer_group_id.