Does adding children's names to the deeds of a Hong Kong flat involve any duty or tax?

My husband and I have owned our flat here for more than 35 years. For succession planning, we would like to add the names of our two children (living and working abroad) to the title deeds of the property. Would this involve any duty or tax at any stage and, if so, would it be wise to do it in the current financial climate? We are about to start making our wills.

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