How do I change the acquisition date on my 1099B to reflect the correct date?

[mltowle]

I need to adjust the cost basis, as I have held this stock since 1998. Can I take the average of dividend years on which Ive paid taxes on the dividends?

[VolvoGirl]

If you reinvested the dividends that adds to the cost basis so you don’t get taxed again when you sell.  A reinvested dividend is really 2 transactions, a dividend and a buy.  You got a Dividend and then you bought more shares.

Then you might have to split the sale into long term and short term for any dividends reinvested within the last year.

[DianeW777]

It depends. The only time averaging is allowed, in tax law, is when it comes to investment sales for mutual funds. 

If your investment is mutual funds then you are allowed to take the average of your total cost, including reinvested dividends, to determine your cost basis for the sale. Take your average cost times the number of shares or units sold to arrive at your actual cost for your investment sale in 2025. 

If you are selling stocks and not mutual funds, the the cost basis must be your actual investment including reinvested dividends for the shares sold.

If not indicated on your statement, you must know which are long term and which are short term holdings.

@mltowle