# Description

**Steps to Reproduce**

1. Install Belgium Localization, then go to **Settings → Accounting/Invoicing**.
2. Enable **Verify VAT Numbers** (`vat_check_vies`).
3. Go to **Accounting → Configuration → Fiscal Positions** and confirm or create an **Intra-Community** fiscal position with:
   - Detect Automatically (`auto_apply`): enabled
   - VAT Required (`vat_required`): enabled
   - Country Group: EU, no specific country configured
4. Open an incognito/private browser window and make sure the session is unauthenticated.
5. Go to the website's `/shop` page and add any product to the cart.
6. Proceed to checkout until reaching the Address step (`/shop/address`).
7. Enter a delivery address in an EU country different from the company's country (e.g. company in Belgium, delivery address in the Netherlands).
8. In the VAT Number field, enter a real, valid, VIES-registered VAT number corresponding to the delivery country (e.g. a valid NL VAT number for a Netherlands address).
9. Click **Save Address / Continue** and proceed to the Payment step (`/shop/payment`).
10. Check the tax applied to the delivery line and the resulting order total.

**Issue**

The delivery product and the overall order are taxed at the standard/domestic VAT rate instead of the expected 0% intra-community rate — even though the customer provided a valid, VIES-registered EU VAT number matching the delivery country.

**Root Cause**

In `base_vat`, `res.partner.create()` unconditionally removes `vies_valid` from the ORM's pending computation queue via `env.remove_to_compute()`, relying on a subsequent `write()` to trigger the actual VIES check. This holds for the standard backend flow, where creation is followed by a `write()` — but the website guest checkout flow differs:

- `website_sale` creates the guest partner through `_create_new_address()`.
- The partner is created via a single `create()` call, with no follow-up `write()`.
- `_compute_vies_valid()` is therefore never triggered.
- `vies_valid` remains permanently unset (`NULL`), despite a VAT number being provided.

Downstream, `account.fiscal.position._get_vat_required_valid()` reads this unset value as falsy, so the Intra-Community fiscal position's `vat_required` condition fails and is rejected in favor of another applicable position (e.g. EU B2C or Domestic).

**Solution**

After partner creation, explicitly trigger `_compute_vies_valid()` when the partner has a VAT number and the operation is not part of a file import (`import_file` context) — performing the VIES check immediately instead of relying on a `write()` that guest checkout never issues.

**Result**

Guest customers providing a valid EU VAT number now get `vies_valid` computed immediately at creation. Fiscal position detection correctly identifies the Intra-Community position, and the expected 0% VAT treatment is applied to the delivery and order.

OPW: 6522992

Forward-Port-Of: odoo/odoo#286201