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. A broker must report it for identical covered securities (same CUSIP) inside that one account; it is allowed to report more. That single-account minimum isn't your broker being lazy; it's what the broker-reporting regulations require, and no broker can see your accounts at other brokers.

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.

What box 1g may leave out

• Cross-broker washes — a broker can't see your accounts at other brokers (the cross-account trap).
• Spousal-account washes — Pub 550 makes a spouse's re-buy your wash sale, with no filing-status condition, and a broker isn't required to report it (details).
• IRA absorptions — the worst case: permanently disallowed per Rev. Rul. 2008-5, and a broker isn't required to report it on the 1099-B.
• Substantially-identical-but-not-identical cases, like buying a call after selling the stock: the call has its own CUSIP, so a broker isn't required to report it (where the line is).

Reconciling it

Box 1g is what that broker reported. It can be higher or lower than the all-accounts figure, so compare them instead of assuming either one is right. If the correct disallowed amount differs, the Form 8949 instructions (code W) have you enter the correct amount in column (g), and if it is lower than box 1g, attach a statement explaining the difference (where it goes). To see the difference: 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.

Numbers that don't match? See what to check when your 1099-B differs from your records.