Why does the adjusted cost basis increase past the stocks original purchase price upon selling in my tax document? There seems to be some discrepancy between my transaction history and my tax document. Two questions:

I. Why does the tax document show a greater loss than my transaction history?
II. What was the raw amount of cash I lost that day, i.e. ignore taxes?

On a particular stock:
My tax document suggests a loss of $4,672.
My transaction history suggests a loss of $1,315.

Note, all trades were within the same day on the same stock.

Mock Tax Document:
Tax Document ($-4,672)

Why does the total cost basis when selling seemingly magically increase past the original total cost basis when buying? The amount column suggests a lost $1,315, while the realized gain/loss column suggests a lost $4,672.

Mock Transaction History:
Transaction History ($-1,315)

I remember loosing around $1,315 that day. The total funds in my brokerage account suggest I lost $1,315 that day. The brokerage account guy I spoke with on the phone said I lost $4,672. I told him several times that I wanted to know the raw amount of cash I lost, and not all this tax disallowed loss mumbo jumbo. He still claimed I lost $4,672. I disagree. Who is right?

Suggestions on how to improve the clarity of this question will be acted on.

  • Tax questions require a country tag. Where are you? Commented Feb 17, 2020 at 1:00

2 Answers 2


An increase in cost basis is most likely a wash-sale adjustment.

There can be intermediate wash-sales even when there is no ultimate wash-sale and there can be same-day wash-sales.

The figures on the 1099-B don't get corrected, for instance to no-ultimate-wash-sale, until they are tabulated on an 8949.

For instance on a 1099-B, a loss on the first trade of a position is a loss in the gain/loss column. When a second trade is opened within 30 days then the positive amount of the loss on the first trade is added to the basis of the second trade. Then a loss on the second trade puts a cumulative loss in the gain/loss column. When a third trade is opened within 30 days then the positive value of that cumulative loss is added to the basis of the third trade. Then say that the third trade is overall profitable and that puts the net position gain in the gain/loss column. Now the sum of the gain/loss column is not very useful because each gain/loss item of the wash-sale section is a cumulative net.

  • That actually helped a lot! So, my actual loss is $1,315, i.e. the max row in the gain/loss column. The gain/lost column is a sum in this case. The $4,672 is meaningless. Sound correct? Thanks S Spring. Commented Feb 18, 2020 at 1:15
  • There's a viewpoint that overcomes the confusion of the intermediate wash-sale accounting and that's Proceeds - Cost + Wash-Sales.
    – S Spring
    Commented Jul 1, 2021 at 21:19

You stated that all of these trades occurred on the same day. If it's is simple as that then your calculation is correct.

However, there is the possibility that you have other trades and positions in this stock within 60 days of the trading day in question (30 days before and 30 days after). If so, there could be a wash sale violation, resulting in the broker's calculation being correct. This assumes that an open position with a wash sale violation is carried over into the subsequent year. I suspect that this might be a possibility because you mentioned "tax disallowed loss mumbo jumbo".

If you want an accurate answer, you need to provide all trades in this stock in sequential order along with the transaction dates.

  • Thanks Bob! All the same stock on the same day. I updated the figures. I know what a washout disallowed loss is. My question moreso is – (1) Why does the total cost bases seem to magically go up beyond my original purchase price upon selling, and (2) what was my actual loss? Commented Feb 16, 2020 at 21:05
  • If you have no wash sale violation carry forward before these trades and no wash sale violation after these trades (extending across the end of the tax year) then the broker's calculation is incorrect. Commented Feb 16, 2020 at 22:57

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .