The easiest route is to visit the website where you have taxable investments now, and look for a "cost basis" area that shows what you paid for each investment. Or maybe you can look at the history, and add up each purchase. Think of "cost basis" as your cost, and anything above that is a gain.
If some funds have a negative cost basis, you can sell them now and switch those to Vanguard. You can look up "tax loss harvesting" to read about how people do this as a strategy. Although stocks are up, you might peek at your bond funds to see if they have a loss.
Most people are in the 15% long-term gains tax rate. So if you had a fund you dislike that gained +$1,000 you're probably paying $150 tax on that gain. You should size up the gains on each fund, to see the impact of selling all of them. You could also sell some now, and sell others later.
I'd suggest:
* sell funds with at a loss first. It's a tax benefit, but avoid buying then selling within 30 days - too soon for the IRS. To avoid this "wash sale", you just wait for day 31.
* sell long-term gains next. These have a better tax rate, 15% for most people.
* you can either sell short-term gains last, or wait for day 366 when they become long-term gains. This will be like ordinary income tax, 25% if you're near the median income.
If it looks like you'll push into another tax bracket with these sales, consider doing half now and half in Jan 2017. Then you'll be taking gains across two separate tax years.
