Nengajo is translated as New Year’s Cards in English and its shortened form, “gajo,” is also used. The custom of sending nengajo traces back to the Meiji period (1868-1912), when postcards were first issued in Japan. Until then, people visited their relatives and acquaintances to greet them at the New Year, but nengajo enabled people to do so by sending cards. Now with the popularization of the Internet, more and more people send nengajo online. At shops you can buy ready-made nengajo with text and pictures printed on them or order original ones. Toward the end of the year, you may ask your Japanese co-worker if he or she has finished writing nengajo by saying, “Nengajo wa kakimashitaka?” But remember this expression can be used only in December.
Sending nengajo to business partners and client companies is still widely practiced in Japan. Online greeting is ok among friends. But on business, it is still probably a must to use this old style way of expressing gratitude with one another.