1099-B box 1g: what your broker's wash-sale number covers

Box 1g of Form 1099-B is the wash-sale loss your broker disallowed during the year — computed only for identical securities (same CUSIP) inside that one account. That single-account scope isn't your broker being lazy; it's exactly what the broker-reporting regulations require, and it's all any broker can see.

Included in box 1g

• Same-ticker re-buys inside the 61-day window, in that account — including DRIP purchases.
• The cumulative disallowance across a year of churning, which is why the number can look enormous — see why 1g can dwarf your real losses.

Structurally missing from box 1g

• Every cross-broker wash — your other accounts don't exist to this broker (the cross-account trap).
• Spousal-account washes for joint filers.
• IRA absorptions — the worst case: permanently disallowed per Rev. Rul. 2008-5 and reported on no form at all.
• Most substantially-identical-but-not-identical cases, like options on the stock (where the line is).

Reconciling it

Treat box 1g as the floor, not the total. The gap between your brokers' 1g numbers and the IRS-level truth is your Form 8949 code-W to-do list (TurboTax steps). To see the gap: drop all your brokers' CSVs into our free checker — it computes the cross-account view in your browser and hands you a year-end summary to compare against each 1099-B.