Someone asks, how do they know? When applying for probate, the executor(s) of the estate will be asked to check the records and declare any substantial gifts that might exceed the allowance. Many executors won't know, and won't be able to match up every Christmas gift recipient against a lump sum received in the same tax year. If smaller payments have been made by different methods (cash, cheque, bank transfer, gifts of Premium Bonds) it'd be almost impossible, and anyway it's not the sort of fraud that HMRC is after. The executor will just report that all is in order, and that'll be an end of it.
So it's not you, the donor, who has to pay tax and give an account of gifts given; nor is it the recipients who are liable for tax . It's on the estate of a deceased person that any tax is levied, and only if IHT is payable, which now applies in only a small percentage of cases, as the allowances are now very generous, and unused allowances can be passed on between spouses.