Inspired by the serendipitous isolation of N-formylpiperazines when we attempted the synthesis of a series of piperazines, we have developed a straightforward methodology for the N- and O- formylation of secondary cyclic amines, anilines and steroids, respectively. Such approach is based on the hitherto non-reported use of DMF·HCl complex, as a versatile and easily-available formylating system that can be stored without apparent loss of activity.