Garnishee denial of liability requires a formal sworn statement and notification to the assessee to enable rebuttal and recovery. Where a garnishee denies liability under section 226(3), the assessee must be notified so the assessee can produce evidence of debt to rebut the denial and enable action. Denials must be by a statement on oath; oral statements or letters are unacceptable. If no proper sworn statement is filed within about a fortnight after the due date, authorities must proceed to recover the amount from the garnishee. These rules apply mutatis mutandis to corresponding provisions in related tax statutes.