Can We write off aloan $26000 we made to our son when he was terribly in debt in 2016-17. There is no way it will be paid back in our lifetime. He signed a note, etc.

[brooks1128]

My son is 45 years old, went through a bankruptcy in 2015, a divorce that just became final and three young boys to support.

[SweetieJean]

"when he was terribly in debt in 2016-17."
 Did you nonetheless have a reasonable expectation that he would be able to repay you?

[SweetieJean]

Without such a reasonable expectation, there could not be a debtor-creditor relationship.
See Litton Bus. Sys., Inc. v. Commissioner, 61 T.C. 367, 377 (l973); CMA Consol., Inc. v. Commissioner, 89 T.C.M. (CCH) 701, 729-30 (2005); Shaw v. Commissioner, 106 T.C.M. (CCH) 54, 56-57 (2013).

[AlanT]

Yes, the bad debt is deductible.  

Please see the following information regarding bad debt and how to report it on your income tax return. 

https://turbotax.intuit.com/tax-tips/irs-tax-return/how-to-report-non-business-bad-debt-on-a-tax-ret...

[SweetieJean]

A nonbusiness bad debt deduction requires a separate detailed statement attached to your return. The statement must contain: a description of the debt, including the amount and the date it became due; the name of the debtor, and any business or family relationship between you and the debtor; the efforts you made to collect the debt; and why you decided the debt was worthless.