Anyone who winds up a deceased person’s affairs must see that all legitimate debts are paid. Claims are received two ways – formally and informally.
At the formal level, the Notice of Petition to Administer Estate published in the newspaper gives legal notice to all creditors to file their claims within four months after issuance of the letters. In some circumstances, however, a creditor may file a claim after the four-month period has expired. Claims must be filed with the court and served on the personal representative, or the claims will be invalid.  In addition, written notice must be given within four months after letters are issued to all known or reasonably ascertainable creditors and you must continue to give notice as you become aware of new creditors.
Informal claims are made when bills come to the decedent’s last address. Probate Code §10552 allows you to pay the debts at your discretion without court approval or without requiring a formal claim if you have independent administration authority. In addition, when there has been a written demand for payment, Probate Code §9154 allows you to pay debts incurred by the decedent before death within 30 days after the claim period ends without requiring a formal claim, unless for some reason you dispute the amount or legitimacy of the debt.