▁six ▁months ▁after ▁the ▁date ▁of ▁issue . ▁The ▁checks ▁worked ▁until ▁the ▁bank ing ▁system ▁was ▁upgrad ed ▁to ▁handle ▁electronic ▁trans fers ▁of ▁large ▁amounts ▁of ▁ đ ồ ng , ▁making ▁most ▁large ▁c ash ▁transactions ▁unnecessary . ▁ ▁Other ▁uses ▁of ▁ đ ồ ng ▁In ▁the ▁Vietnam ese ▁language , ▁" đ ồ ng " ▁can ▁be ▁used ▁as ▁a ▁generic ▁term ▁for ▁any ▁currency ▁by ▁adding ▁the ▁name ▁of ▁a ▁country ▁as ▁a ▁qual ifier . ▁This ▁practice ▁is ▁more ▁common ▁for ▁more ▁es oter ic ▁units ▁of ▁currency . ▁ ▁In ▁present - day ▁Vietnam , ▁when ▁mention ing ▁an ▁amount ▁of ▁money , ▁the ▁currency ▁can ▁be ▁( and ▁usually ▁is ) ▁omitted . ▁ ▁Exchange ▁rate ▁ ▁After ▁the ▁re valu ation ▁of ▁the ▁Z imb ab we an ▁doll ar ▁on ▁ 1 ▁August ▁ 2 0 0 6 , ▁the ▁ đ ồ ng ▁became ▁the ▁least ▁val ued ▁currency ▁unit ▁for ▁months . ▁Ar ound ▁ 2 1 ▁March ▁ 2 0 0 7 , ▁the ▁re valu ed ▁Z imb ab we an ▁doll ar ▁reg ained ▁least ▁val ued ▁currency ▁status ▁( in ▁terms ▁of ▁black ▁market ▁exchange ▁rate ), ▁and ▁on ▁ 7 ▁September ▁ 2 0 0 7 ▁in ▁terms ▁of ▁official ▁exchange ▁rate . ▁After ▁the ▁use ▁of ▁the ▁Z imb ab we an ▁doll ar ▁ceased ▁on ▁ 1 2 ▁April ▁ 2 0 0 9 , ▁the ▁ đ ồ ng ▁was ▁the ▁second