Bibijee,
give Guru Sahib his share, doesn't sound right.
we can never give anything to the ultimate giver of all, and he doesn't have shares,
everything belongs to him.
Guru Saahib doesn't need our earned money. If we give dasvandh, it will be for our good,
because we obeyed Guru Sahibs hukam, and someone got benefit from that money.
i know the question is, do we need to take out daswand from any monitory gift received from family/relatives etc.
if it is not from your kirt kamayee, then i guess you don't have to, but if you have spare from that money, then why not donate it to a good karaj. but i don't believe just because the government might take taxes from that money that you have to give a share to Guru Sahib too.
Bhul Chuk Maaf Karna Jee