As I explained, the "wash sale loss disallowed" is simply the SUM of all your wash sale loss trades. It's NOT a deferred loss you can claim later. Undoubtedly a big part of the wash sale losses is INCLUDED in the basis figure reported on the 1099-B. And, maybe, some of the wash sale loss is embedded in the basis for those January purchases if they were replacement shares associated with December wash sale losses.
Brokers have had to pretty much perfect these systems since the IRS dictated to them how they needed to do their 1099-B reporting back in 2010.
