Is an informal marriage contract, concluded with two witnesses, an offer and acceptance, and the father's subsequent approval by signing the contract, considered valid?

If the father does not undertake the marriage contract, nor appoint someone to act on his behalf, and the matter is not rectified, then the contract is invalid according to the majority of scholars, and it must be renewed by the father or his proxy. Subsequent approval by the father does not validate the contract. The contract is valid if a Sharia (definition) judge rules it to be so, or if the contracting party follows Imam Abu Hanifa.