If indeed you simply used "added" transactions then there should be no problem editing those to enter a correct per share cost.However, it would be easier to give to guidance as to what per share cost to use if we understood the employer's "plan" better. "every six month for many years" does sound like an ESPP as that's a commonly used period of time, but even that doesn't give anyone much direction since there are both Qualified and Nonqualifed ESPP plans and the calculation of basis can and usually does vary between the two. Were you contributing any money to get these shares? Was there an impact on your W-2 - compensation - for the stock received? The fact that the shares were not publicly traded certainly doesn't mean the stock has no basis - as you know - but if these were simply "grants" of some amount of stock with no contribution on your part then there should have been a W-2 effect.
You can download up to 5 years of historical prices, but:-- daily prices only go back 1 month, before that they are weekly or monthly.-- the downloaded prices are stored in Quicken's price history, but they do not affect transactions or cost basis, only performance reporting.
I agree with splasher, the total cost of the lot along with number of shares is what gets reported to the IRS for covered securities. Fidelity should have trade confirmations that provide the total cost for the lot.
its six per quarter times 20 years ... thanks for all your help in managing my time.