What are the means of proving entitlement in a financial claim arising from a contract, and what is the effect of documents signed by the representative of the other party?

Entitlement to claim is established by submitting business documents signed by the representative of the other party. These documents are considered binding proof against the signing party, unless the authenticity of the signature or the handwriting attributed to its representative is expressly denied. This is further supported by the other party's acknowledgment of the validity of the contract and its failure to provide a substantive response.