Le lettrage des comptes is a technical French expression which is a reconcilation procedure, similar to what is called in American bookkeeping a tie-out or a prove out. Since it is a unique French procedure of a certain kind of prove out, I would use the English langauge equivalents: lettering, letter and not lettered, which terms will be inteligible in context to the reader.

The lettering, or in this the exception where the entry is not lettered, is a function of computerized accounting system. The computerized processess forces a self audit of vendor and other such accounts.

Having worked in accounting and bookkeeping in the United States for 12 years, I found myself always having to deal with new terms and procedures which were similar but not exactly equivalent. The bookkeeper learns quickly that if he or she wants to get it right that is necessary to understand the precise procedure and purpose of the procedure.