Another approach valid for every actual date regardless the year maybe this?:
=FECHA(AÑO(HOY());RESIDUO(MES(A1)+1;12)+(1-SIGNO(RESIDUO(MES(A1)+1;12)))*12;1) -----> in english: =DATE(YEAR(TODAY()),MOD(MONTH(A1)+1,12)+(1-SIGN(MOD(MONTH(A1)+1,12)))*12,1)