I forgot to put my real estate taxes on my 2018 return how do I correct it when I sent e file already

[Texas Roger]

Once you submit your return to TurboTax for efiling, it is just like dropping your return in the mailbox--you can't get it back. If the IRS rejects your return, you can make the changes, fix the reason for the rejection and resubmit it. If the IRS accepts your return, you should wait until you receive a refund (if you are getting one) and then you can prepare, print, sign, and mail an amended (changed) return form 1040X to make the changes. Do not change your original return until you begin the amended return.

The only reason to add the real estate taxes on a federal return is if you were able to itemize deductions because they were more than the standard deduction or if by adding the real estate taxes, your itemized deductions would then be more than the standard deduction and it increases your refund or reduces taxes owed. There is a $10,000 limit for 2018 in the amount of SALT taxes than can be deducted. These taxes include real estate and state and local income taxes or state and local sales taxes. 

If you file state taxes and itemize deductions, there might be a benefit on your state tax return even if there is none on your federal return.