If you are filing an extension, be aware that taxes are due on the original tax deadline although you are filing an extension. Although the penalty for 'Failure-to-Pay' is less than the 'Failure-to-File' penalty, the penalty and interest can add up if you wait until later to pay your taxes you owe.
People who inherit 401(k) plans often face challenges obtaining account information. Persistence in contacting financial institutions is essential for beneficiaries to access funds.