The highest weight would probably be given to documents that are signed, dated, and witnessed. In practice, however, the legal system accepts that the degree of formality associated with a document will depend on the importance of the record. Very formal records, such as wills, are formally signed and dated. At the other extreme, file notes may be accepted even though they have neither a signature nor a date. The courts may, of course, give different weights to documents with different degrees of formality.
Business records are an exception to the hearsay rule, and are assumed to be 'reliable hearsay'.
Authenticity of unsigned and undated records can be conferred by the fact that they were generated and kept as part of the normal business activity. The records are given reasonable weight because if the records were inaccurate they would be useless for the business purpose for which they are kept. Signatures are important on documents for many reasons. In law, the act of signing a document must be a conscious decision as it effects an act of will. This has implications for the automatic application of digital signatures to documents.