Validation has two stages. The input must first contain only ASCII Roman symbols within a fixed length. Its interpreted value is then encoded again and compared with the normalized uppercase source.
Invalid characters fail at their first position
Spaces, punctuation, decimal digits and Unicode Roman numeral glyphs are not silently trimmed or replaced. The reported one-based position makes the correction reproducible.
Re-encoding proves the selected canonical form
If the re-encoded string differs, the tool returns a noncanonical error with the interpreted value and exact suggestion. Accepting that suggestion runs the complete conversion again.
Verify the receiving convention
RomanClear uses the explicit modern 1–3,999 profile shown on every result. Historical inscriptions, clock faces, editorial house styles and organization-specific conventions may use other forms. Compare important output with the convention required by the document or system that will receive it.