The annuity start date would be the day and year you started receiving distributions from the annuity. The distributions would be entered from a Form 1099-R that you received. You enter that in the Wages and Income section of TurboTax, then Retirement Plans and Social Security, then IRA, 401-k, Pension Plan Withdrawals (1099-R). Work through that section and you will find the annuity entries that you can edit as required.
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