New York State's estate tax is calculated using the tax table provided on Form ET706. There are multiple versions of Form ET-706.The New York estate tax rate is not fixed and follows a progressive structure. You must also attach federal form 706, United States Estate Tax Return. For estates subject to federal estate taxes, IRS Form 706 must be filed within nine months of the decedent's death. Not only do you have to file the decedent's final income taxes, but you will also need to file an income tax return for the estate itself.