Many countries have a tax on buying bullion, but also for selling it as well. When planning to buy bullion, it's important to think of your exit strategy. You'll want to record your purchases because you'll likely end up paying a capital gains tax if you sell any of your bullion and make a profit.
You'll want to check your country and state/region/province laws to identify if you pay taxes on purchases, sales, or both.
Using the US as an example, even though your state may not charge taxes on bullion purchases, what you buy may trigger required reporting to the IRS. JM Bullion has a great graphic that explains it well. Click here to check it out.
Any sale of bullion in the US incurs a 28% capital gains tax on any profit you make from selling it. You'd want to account for that in any bullion you're selling, or you could end up seeing your after-taxes profits sharply reduced, as you may not be making as much as you thought once taxes are deducted.
Even if you plan to hand some down to the next generation in your family, make sure they're also aware of this for when they go to sell it, or even buying it if they choose to stack bullion as well. Planning your exit strategy is just as important as timing your purchases, so make sure you set aside some time to plan this out, discuss it with your partner or spouse, and include your kids and/or other heirs if they're old enough to understand.