Hi @anxiousoldie,
It can be confusing, but registering a testamentary trust doesn’t mean selecting 'deceased estate' again - they're treated as separate tax entities. The difference is about timing:
A deceased estate exists while the executor is administering the estate. If the estate earns income during this period, you apply for a TFN for the deceased estate.
A testamentary trust is a trust created by the will. Once assets are transferred into the trust and it starts operating, it needs its own TFN. From a tax perspective, a testamentary trust is usually treated as a trust established by a will and often operates like a discretionary trust.
If you’re unsure which stage you’re at, it usually comes down to whether the estate is still being administered or whether assets have already been transferred into the trust. The links above should help with guides and steps when it comes to estate planning.