(a) A claim against the estate of a decedent or ward, whether based on contract, tort, statutory custodial claim or otherwise, may be filed with the representative or the court or both. When a claim is filed with the representative but not with the court, the representative may file the claim with the court but has no duty to do so.
     (b) Within 10 days after a claimant files his claim with the court, the claimant (1) shall cause a copy of the claim to be mailed or delivered to each representative to whom letters of office have been issued and not revoked, including the guardian of the person of a ward and to the representative’s attorney of record, unless the representative or the attorney has in writing either consented to allowance of the claim or waived mailing or delivery of a copy, and (2) shall file with the court proof of any required mailing or delivery of copies. Failure to mail or deliver copies of the claim or to file proof thereof does not affect the validity of the claim filing under subsection 18-1(a).