My charitable contribution was postmarked 12/31/2018 and cashed in January of 2019. Am I required to count this deduction for 2018, or can I deduct it in 2019 instead?

[user861698]

I am planning to take the standard deduction in 2018, but I will have a new mortgage in 2019 and enough deductible mortgage interest that I expect to itemize in 2019.

[JohnW15]

If you mail a check or money order to a charity, the contribution is considered to have been made on the date you mailed it.  So, if your letter was postmarked 12/31/2018 then, unfortunately, you can only claim the contribution on your tax year 2018 return.