First Offence definition limits compounding of category B offences; timing and voluntary disclosure determine eligibility. First Offence for Category B offences is when the offence was committed before the earliest of issuance of any prosecution-related letter or notice, intimation of prosecution complaint filing sent by the department, or launching of prosecution; it also includes offences not detected by the department but voluntarily disclosed by the assessee via a compounding application. The first offence is assessed only where committed by the same person or entity and is determined separately for each Category B offence.