Spouse died several years ago, paid estate taxes that included an irrevocable trust among other assets.  That trust was closed and with the remaining income, a new irrevocable trust was formed naming the surviving spouse and daughter as co-trustees.  When the surviving spouse died, the irrevocable trust went directly to the daughter.  There was no need for probate since it was stated in the trust agreement that the daughter was to inherit the trust upon the death of the surviving spouse.  It was also stated in the agreement that the surviving spouse was entitled to the income, within limits, until her death.  My question is does the surviving spouse need to include 50% of the value of the trust in her estate when filing the Estate tax return.