I recently joined and have a Gold Membership but I'd like to upgrade to Platinum...mainly so I can get the physical copy of The Numismatist magazine... Do I have to wait until my renewal date or can I pay the difference to upgrade..

I imagine it's possible to upgrade; try contacting the ANA and asking about it, I'm sure they could help you:  membership@money.org

You can always upgrade and/or renew early, especially now with them screaming for ways to replace lost income from effects of Covid-19.  Just contact them through customer service or the web site.  

Go right ahead. There waiting for your money now!! Yes you can. There should be no problem. .

Thanks for the responses!  I'll give them a call...

When you upgrade, be sure to get that signed silver eagle coin! I just paid for 3 years, and will receive the signed silver eagle. 

I'm going to write a blog on the president who signed my coin's label. Hope others will as well...