There are a lot of considerations to take into account when setting up a gift to a person with disabilities. If that person is receiving disability benefits, you will want to make sure your gift to them does not disqualify them from receiving those benefits. If the child with disabilities receives a lump sum gift, depending on the amount of the gift, they may no longer pass the strict income and asset requirements that determine whether or not they will receive their disability benefits. Even if the child is not receiving disability benefits, you may want to appoint someone as their trustee to handle their money for their benefit. You can also do some planning outside of your will with tools such as registered disability savings plans.
