Income tax: can a trustee quote the trust Tax File Number (TFN) to an investment body when an investment of the trust estate is held in the trustee's name?

Yes. Subsections 202D(6) and (7) of the Income Tax Assessment Act 1936 specifically allow a person making an investment in their capacity as a trustee of a trust estate to quote the trust TFN. This applies even though the account is held in the name of the trustee.