A valid e-invoice file is a UBL 2.1 or CII XML containing the RO_CIUS customisation identifier, invoice number and date, tax IDs for the supplier and buyer, currency, line items, and totals. The validator checks these elements locally in your browser without uploading the file anywhere.
No. The validation runs entirely in your browser; the file is not uploaded or stored anywhere.
No. This is a preliminary check to catch common structural errors. Official validation is still performed by the national tax authority via SPV.
XML UBL 2.1 (Invoice) and CII (CrossIndustryInvoice), specifically the versions used in RO_CIUS.