What invoice field validation checks
Field validation finds missing or inconsistent application inputs. It does not verify an invoice against EN 16931, a country profile, a tax registry or recipient rules.
Required information
Invoice number, issue date, due date, seller and buyer names and addresses, and at least one described line item are required. The creator checks supported currency and country selections, valid calendar dates, due-date order and the shape of optional email addresses.
Numeric and tax checks
Quantities must be positive. Prices must be non-negative. Discount and tax percentages must fall between 0 and 100. The creator rejects unsupported decimal precision and requires zero tax for zero-rated, exempt and outside-scope categories. Exempt and outside-scope items also need a reason.
What passing does not mean
A passed field check means the required application inputs are complete. It does not establish that a tax rate is correct, a tax identifier exists, the invoice number is unique, payment instructions are valid, or the output meets country-specific or recipient-specific requirements. Review those separately.
Planned formal validation
A future standards adapter needs an explicit data mapping, schema validation and applicable business-rule checks. Only formats that have been implemented and verified will be presented as standards-supported.