You can't get a power of attorney to act for someone after he's died, and an existing power of attorney becomes invalid upon the death of the principal—the individual who gave you the right to take certain actions on his behalf.
Someone is still going to have to take care of his affairs after his death, but it won't necessarily be the agent appointed in a power of attorney during his lifetime.
If You Were the Deceased's Agent
Perhaps your parent recently passed and you were named as his agent in a power of attorney (POA). You're the individual he wanted to take care of certain personal business matters for him. The POA gave you the authority to act on his behalf in a number of financial situations, such as buying or selling a property for him or maybe just paying his bills.
You might think that you should continue paying those bills and settling his accounts after his death, but you should not and you can't—at least not unless you've also been named as the executor of his estate in his will, or the court appoints as administrator of his estate if he didn't leave a will.
When There's a Will
People can no longer legally own property after they're deceased, so probate is required to transfer their property to living heirs. Your parent's will must, therefore, be filed with the probate court shortly after his death if he held a bank account or any other property in his sole name.
This begins the probate process to legally distribute his property to his living beneficiaries. The executor named in his will is responsible for doing so and guiding the estate through the probate process.
When There's Not a Will
The deceased's property must still pass through probate to accomplish the transfer of ownership, even if he didn't leave a will. The major difference is that his property will pass according to state law rather than according to his wishes as explained in a will.
The court will appoint an administrator to settle the estate if the deceased didn't leave a will. You can apply to the court to be appointed as administrator, and the court is likely to agree if the deceased left no surviving spouse, or if his surviving spouse and his other children agree that you should do the job.
Estate Executor vs. POA Agent
In either case, with or without a will, the probate court will grant the authority to act on a deceased person's estate to an individual who might or might not also be the agent under the power of attorney. The two roles are divided by the event of the death. In some cases, however, the agent in the POA might also be named as executor or administrator of the estate.
You would continue to have authority over the deceased's bank accounts and other assets if you're also named as the executor or administrator, at least until ownership can be transferred to living individuals.
The Power of Attorney After Death
The POA you hold for your parent is useless and serves no purpose after his death. The deceased person no longer owns anything for you to handle for him because he can't legally hold money or property.
The POA might authorize you to make financial transactions for him, but he technically no longer owns the property or the money over which the POA placed you in charge. His estate owns it, so only the executor or the administrator of his estate can deal with it during the probate process.
As a practical matter, most financial institutions immediately freeze the accounts of deceased individuals when they learn of their deaths. The freeze remains in place until they're contacted by the executor or administrator of the estate. If you were to attempt to use the POA, it would be denied.
Exceptions to the Usual Rule
Some very small estates don't require probate, or your parent might have used a living trust as her estate-planning method rather than a last will and testament so probate would not be required. A successor trustee would take over after the deceased's death if he left a revocable living trust, but these exceptions are limited.
The POA becomes invalid in both cases anyway.
It can also change things if your parent's bank account or other property is not included in his probate estate for some reason. Probate is only necessary for assets that your parent owns in his sole name. These assets require a legal process to transfer to living beneficiaries.
But if your parent listed you as co-owner of his bank account or even on the deed to his home, giving you "rights of survivorship," the account or the property passes automatically and directly to you at his death. Probate of these assets would not be necessary.
You would retain control over these assets, but you would no longer be responsible for paying your parent's debts from that money because probate also handles his final bills. You would be responsible for paying debts on which you co-signed with the deceased, just as you were during his lifetime.