Excuse me, I didn't quite understand what you meant. I've accumulated this sum of bitcoin through a variety of sources. I haven't bought a single one. Theoretically, isn't this income something that should be declared? I'm talking about the whole amount of coins.
What I meant is that it's only you who knows where you've got those coins from and whether it's by working for them, or mined, or you've bought them long ago when KYC was not everywhere. And I don't think that anybody would invest too much of resources to find out if your declaration is for real or it's hiding a bit of details here and there.
Hence if you declare them as income then you'll probably pay income tax and if you declare them as capital gains (from 0 since you don't have receipts), then you'll pay capital gains tax.
That's how I see the things.
It won't be suspicious if he/she has a business or high paying job to cover perhaps a huge amount to enter his/her account if ever he will be selling some of his/her crypto assets. Declaring it would be somewhat foolish especially if this industry is not having a wide support. It happened to my friend. Since he's unemployed his account was questioned when a huge amount was deposited mid last year which forced him to move to another one but decided to hide half of his welath under his brother's name which is a businessman, with consent ofcourse. If this is what is meant of declaration then think twice. But if it is just verbally sharing to other people, I see no other problem than to be at risk of being targeted by bad guys out there.