With the Tax Reform changes that started in 2018, the standard deduction increased quite substantially and, if the standard deduction amount is more than your itemized deduction amount, TurboTax will recommend the standard deduction as it will be more favorable to your tax situation.

For 2018, the standard deduction amounts are $12,000 for single/married filing separate, $18,000 for head of household and $24,000 for married filing joint (plus additional amounts for over 65 and/or blind).  Therefore, to benefit from itemizing deductions, your itemized total would need to be over those  standard deduction amounts. 

Note that in 2017, the standard deduction was quite a bit lower: $6,350 for single/married filing separate and $12,700 for filing joint, so for 2018 the standard deduction amounts almost doubled.

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