I assume therefore that you dutifully calculate and pay income tax on any and all birthday or Christmas presents?
In the UK there's inheritance tax to pay over a threshold if you die within 7 years of making the gift, but otherwise there's not a 'gift tax'.
The situation you describe still isn't the same as declaring it as income though - assuming you are working, if it were taxed at your marginal rate of income tax you'd already be over any threshold no matter how small the gift.