Once the administration of the estate has been completed, the executor's role becomes a role of trustee in relation to the administration of any ongoing trusts pursuant to the terms of the will. Alternatively, other persons may be appointed as trustee of any ongoing trusts.

The will must specify in full detail all the various powers and discretions that are to be available to the trustees. This is necessary to satisfy the application of the so-called "rule against delegation of testamentary power".

The will might specifically include a power to amend the terms of any ongoing trusts established under the will. An important issue is whether or not the exercise of such power may be invalidated by the application of the rule against delegation of testamentary power. This is because the trustee of the trust will prima facie have power to amend the terms of the trust and therefore of the will under which it was established.

Where any specialised testamentary trusts are included in the will (particularly discretionary trusts), it is considered that the full range of powers that are usually made available to the trustee of an inter vivos discretionary family trust should also be included in the will.

See Trustee powers.

It is essential for the will to confer upon the executors and trustees of the will sufficiently wide and flexible powers so as to be able to fully and properly carry out their duties in administering the client's estate.

There are some cases in which it will be important for the client to give particular powers and directions to the executors, especially as regards the discharge of a debt in relation to an asset, such as a mortgage over the principal place of residence at the date of death.

Often the client will give directions in relation to the exercise of certain powers and rights that the executors may come to have by virtue of the nature of the assets of the estate (for instance, voting rights where the client owns a majority shareholding in a family company).

See Executor powers.