Noun
a letter sent along with other documents to provide additional information
Source: WordNet“In fact on December 23 we sent a thick file to the National Treasury accompanied by a covering letter from our chairman (Ben Ngubane), showing that we have indeed complied with all the conditions. Source: Internet
If you are entering by email or post then state in the covering letter that you are using the pen name of A.N. Other, but that your real name is B.A. Writer. Source: Internet