According to the relevant provisions of the Regulations for the Implementation of the Bidding Law and the Interim Provisions on the Bid Evaluation Committee and Evaluation Methods, the bid evaluation committee will reject its bid without the seal of the bidder and the signature of the person in charge of the unit. But the premise here is that there is neither the seal of the unit nor the signature of the person in charge of the unit, so as long as one of the two conditions is met, the bidding documents should be valid. However, it should be noted that this is only a general case. Sometimes, the tender documents will require the signature of the person in charge and the seal of the company at the same time, so both requirements must be met, otherwise it will be assessed as not conforming to the format stipulated in the tender documents and will be deemed invalid. Therefore, when making bidding documents, you should read the requirements of preparation, sealing and delivery of bidding documents in detail to avoid unnecessary negligence and invalid bidding.