142:8 One should not perform acts of labor (melacha) on Purim. One who does will never see any benefit from it. It is permitted to perform acts of labor through a non-Jew. One may go about his business activities; we may also write, even personal correspondence. One may go over his accounts and do anything that does not require a great deal of concentration. One may certainly write for the purposes of a mitzvah and do any activity required for a commandment. One is also allowed to perform even acts that are pure forms of labor if they are necessary for Purim itself (or if he needs to earn money for food – Shaar HaTziyon 696:2).
142:9 The fifteenth day of Adar is called Shushan Purim. We do not say Tachanun, (k)Eil erech apayim, or Lamnatzeiach on that day.
It is also prohibited to deliver a eulogy and to fast on Shushan Purim (except for a fast one undertakes because of a bad dream – Mishnah Brurah 696:9; 695:6). The practice is to have some feasting and joy but we do not recite “Al HaNisim.” (If one accidentally said it, he does not have to go back – MB 693:6.) One may get married on Shushan Purim because we don’t read the Megillah; we do not hold weddings on the day on which we read the Megillah because that is the core of the celebration and we do not combine one celebration with another. (Mishnah Brurah 696:28 says that we are permitted to get married on Purim.)