Given that you haven't reported taxes on that don't be surprised if the gov't doesn't come looking for you. Given back taxes and interest accrued, you'll probably lose at least 100-150k of the interest. Also, if it doubled and then some in 6 years...it was paying ~13% interest compounded annually which sounds fishy.

Even if the account is running 13% interest, how are you going to retire on 250-300k which should be your share. If you're 26, your life expectancy is at least 70 putting you at 44 years of retirement conservatively given modern medicine. If you can somehow keep that 13% interest flowing on 250k, w/o tapping into the principle, you will see 30k a year pre-tax which is a poor lifestyle and that won't increase w/ inflation. By the end, your 30k annually will be worth something like $4,800 of today's dollars if you follow historical inflation. If you blow it all, you're looking at 5-6 years max before you have to work again. Not trying to kill your excitement but I'd work another 10 years which would put that account at a nice round 2 million once again assuming this mythical 13% your claiming. That gives you a nice round million to work w/ and 80k per year if you put it into safe investments that yield 8% assuming the account you're in isn't liquid and at 13% I don't think it could be.