Unpaid taxes are unpaid debts to the public. You cannot defer your debts without acceptable reasons.
For the calculation, let’s assume that you have 100 gr. of gold.
Tax of the 1st year: 2.5% of 100 gr. of gold is 2.5 gr. and it leaves you 97.5 gr.
Tax of the 2nd year: 2.5% of 97.5 gr. of gold is 2.43 gr. and it leaves you 95.07 gr.
Tax of the 3rd year: 2.5% of 95.07 gr. of gold is 2.37 gr.
We have calculated a total of 7.3 gr. tax for 100 gr. of gold. Now you can make the real calculation for your gold according to this ratio.
It doesn’t matter if you give it as gold or cash while giving.