What, if anything can I do so that my son does not have to pay Inheritance tax on my homes?

You really need to sit down with a lawyer and only make sure you give all of the facts to him or her. This is a decision that should be carefully made. Generally, the only way to avoid inheritance tax is to replace your name on the deed with his. If you put him on the deed with you it will reduce the amount you pay inheritance tax on by half, 175k. Again, get legal advice on this.