When someone passes on, their social security number is retired. A final tax return is filed, and that’s it. So, an estate of deceased is going to need a tax ID / EIN number of its own, because it can no longer use the deceased’s number.
A deceased’s estate may carry on for some time, because the estate needs to be cared for during the process of liquidation, and it may take some time to dissolve the estate. Assets may need to be sold to pay debts. If a will is contested, the state of the deceased could last for years. It may need to hire individuals such as lawyers to figure out the will, and it may need to pay debts such as mortgages. An estate of the deceased can even carry with it complex assets such as shares in a company, and will therefore have to file its own tax return until it’s dissolved.
Usually, the executor of the will and those who are otherwise responsible for the estate will take care of creating the estate and tax ID. An estate attorney can help.