Literal Contract
In the time of Justinian there were no contracts that derived their legal force from the fact that they were in writing, or were written in any particular form. But during the Republic there existed a form of contract made in writing (literis) in the form of an entry in the account book (codex) of the creditor.
This form of contract probably originated in the importance attached by the Romans to their books of account. The Romans were great book-keepers. Every well-to-do Roman kept his domestic account books just as a modern business man keeps his business books. We are told that the censor, at the making of the census, required every citizen to take an oath that his books were accurately and honestly kept.
The literal contract consisted in an entry (expensilatio or nomen transscripticum) made by the creditor in his account book, with the consent of the debtor, to the effect that he had paid a certain amount to the debtor.
The debtor usually made a corresponding entry in his book that he had received the sum stated, but this appears to have constituted no part of the contract and to have been unnecessary. The debtor's liability depended upon the creditor's entry alone. This created the obligation, and was not merely the evidence of an existing obligation. It was the entry of a fictitious payment, but, of course, it doubtless represented some actual transaction not amounting in itself to a legal contract.
The exact details of this form of contract, how this particular entry differed from other entries in the account book, etc., have not come down to us. It is probable that the literal contract was usually employed, not for the purpose of originating an obligation, but of transforming an existing obligation, perhaps not in legal form, into a legal obligation based upon an entry in the account book.