>How long can I keep income, to give him tax free, before it is classed as savings? As soon as it's in the bank it's savings. If it's under the mattress it's not savings but will forgo interest
I am confused by the statements in your question, Reverend. If you wait 20 years to give it you might pay tax on the savings if it's outside an ISA and above the threshold of £1000 for a basic rate tax payer. if you give it your son on tuesday and and he puts it in the bank on Thursday he would pay interest if his savings income exceeds £1000 if a basic rate tax payer.
If you are referring to IHT it's paid by the estate and is only a factor if the estate is over something like £650000 for a married couple, but there are so many exemptions and it's unlikely past gifts would b picked up anyway unless they were substantial.