form 8949 misreported

[ding30749]

hello, I sent to my brokerage company my physical stock certificates and they were issued many years ago (at least 10 years).  I sold the certificates and the brokerage company issued a form 8949 for short term gains.  The brokerage company base the short term gains on the receipt of the stock to their company instead of the issuance date of the phyiscal stock .  Clearly these stock certificates were stamped and issued many years ago  How can I demonstrate to the IRS these were long term gains.

[rjs]

Enter the sale in TurboTax as it is reported by the brokerage, including selecting short-term for the "sales section." After you enter the details of the sale, click Continue. On the next screen check the box that says "I need to correct the holding period reported on my 1099-B." That will change it to long-term, with an adjustment code T in column (f) of the Form 8949 in your tax return. The code T notifies the IRS that the holding period reported by the broker was wrong. You do not send any proof or other information with your tax return.