A boy born on א כסלו תשעב which that year חשון was a חסר. This year תשפה חשון is a מלא. When does he become מחויב במצות on, א כסלו or ל חשון?
He is mechuyav bemitzvos starting on ל חשון, but should not get an aliya, be counted for a minyan or be chazan until א כסלו. Sources: ראה שו״ת…