Frequently Asked Questions

A VAT (Value Added Tax) number is a unique identifier assigned to businesses registered for VAT within the EU. It's used on invoices for intra-EU supplies of goods and services. For zero-rated (reverse charge) transactions, you must verify your customer's VAT number is valid before applying 0% VAT — otherwise you may owe the full VAT amount to your tax authority.

This means VIES online validation was disabled (toggle in the tool) or skipped. The number passed local format validation for its country, but was not checked against the live VIES registry. Enable VIES validation for a definitive result.

Yes. A number may match the correct format (right length, check digit) but not correspond to any registered company. This happens when a business has deregistered, the number was never issued, or the format is correct but the digits are wrong. Always use VIES to get a live registry check.

IČO is the Czech company registration number (8-digit ID for any legal entity). DIČ is the Czech VAT number — for most companies it is "CZ" + IČO (e.g. CZ27074358). Only VAT-registered businesses have a DIČ. avat.app accepts both formats automatically.

VIES (VAT Information Exchange System) is the EU's official VAT validation system. Rather than holding a central database, each query is routed in real time to the national tax registry of the relevant country — making it the authoritative source, but also meaning that downtime in one country's system appears as a VIES error.

VIES failures are common and usually temporary. They occur when: (1) a country's national database is offline for scheduled maintenance, (2) VIES experiences peak traffic (typically early morning in CET), (3) you're querying too many numbers in quick succession (MAX_CONCURRENT error). Use the "Retry Errors" button to re-check failed entries after a short wait.

VIES uses EL for Greece because EU tax systems adopted the code from "Ellada" (the Greek name for Greece) before ISO 3166-1 standardized on GR. This is a historical quirk. When entering a Greek VAT number, use EL — not GR — as the prefix.

An unreliable payer (nespolehlivý plátce DPH) is a Czech VAT-registered company that the Czech Financial Administration has flagged for serious tax non-compliance — typically for failing to file VAT returns or pay VAT obligations. If you pay such a company to an account that is not in the official registry, you may be jointly liable for their unpaid VAT under §109 of the Czech VAT Act.

ARES (Administrativní registr ekonomických subjektů) is the Czech business registry. For Czech numbers, avat.app queries ARES first for company name and address data. The Czech Tax Authority (MFCR) is then queried to confirm the current DPH registration status — this step also catches entities that were once VAT payers but have since deregistered (their end date is set). If ARES returns no result (e.g. for natural persons), MFCR is queried directly. VIES is used only as a last resort or for Czech group registrations.

Yes. Czech group VAT numbers (those starting with 699) are handled correctly — they are checked directly via VIES (not ARES), since group registrations are not individual entities in the ARES registry.

The published account registry (registry of registered bank accounts for VAT payers) is a Czech-specific legal requirement under the Czech VAT Act. No equivalent EU-wide registry exists. The Czech MFCR publishes the accounts that Czech VAT payers have declared for receiving payments. The IBAN checker verifies whether a given account is in this registry — which only exists for Czech entities.

It means the bank account or IBAN you entered is not among the accounts that the Czech VAT payer has registered with the MFCR for receiving payments. This could mean: (1) the company uses a different account for VAT purposes, (2) the account was recently changed and not yet updated in the registry, or (3) the account details you have are incorrect.

No. VAT numbers, company names, and account details you query are not permanently stored. The tool acts as a proxy: your query is forwarded to the official registry (VIES, ARES, MFCR) and the response is returned to you. No history is retained after your session ends.

VAT numbers and company data queried via avat.app are public business registration data from EU and Czech government registries — not personal data under GDPR. No user accounts, personal information, or query history are collected or stored.

The tool supports up to 500 VAT numbers per run, processed in parallel batches (default: 8 at a time). For larger lists, split them into multiple batches. Reduce the batch size in advanced settings to avoid VIES rate-limit errors. Use the "Retry Errors" function to recover from any failures.

VAT validation results can be exported as: CSV (semicolon-separated, UTF-8 with BOM, Excel-compatible), XLSX (formatted workbook with frozen headers, autofilter, company data), and PDF (printable report with summary statistics and validation table). IBAN results support CSV and XLSX export.

API access is planned for a future release. The current tool runs as a local Python server, making it suitable for direct use by finance teams. If you need programmatic access, contact us via the contact page.