Can I put a HDB flat in a trust?
In the event that the original owners pass on leaving the HDB flat to the underage child, the executor/administrator will still need to work with HDB to see if the HDB flat can be placed in a trust till the beneficiary comes of age, and thereafter if he/she is eligible to hold the HDB under one of the schemes. As the testator, you may also write in your Will your intentions to have the HDB sold off first with the proceeds given to your beneficiaries.
You will need to seek approval from HDB if you intend to put the HDB flat in a trust.
The approval for the creation of trust over an HDB flat and transfer are subject to eligibilities and HDB's policy at the point of application. In the case of a testamentary trust, since the trust is not set up yet until the testator dies, HDB is unlikely to be able to give prior approval. What you can do is to make provisions in the case it is not approved. For example, the flat can be sold off with the proceeds to be held in trust instead. You can do this under Additional Instructions within the asset:
If HDB does not approve for this flat to be held in trust, it is to be liquidated with the proceeds held in the said trust.