I understand that Vanguard automatically disallows the wash sale loss. I can see that on my 1099. But what's not clear is whether they automatically add that loss to the cost basis of the repurchased shares? So, if I lost $100 on a stock after selling it, then spent $1,000 buying the same stock the next day, does Vanguard automatically increase my basis to $1,100? Or I need to do that whenever I eventually sell those new shares? I have been trying to look at the adjustments they've made in my account, but I'm coming up with more questions than answers. For example, there is one stock whose shares have been adjusted (according to my cost basis page), but I did not sell that stock or anything remotely similar to it in the preceding 31 days, so I'm baffled why those shares have been adjusted. Thank you!!