Business ABC and Vendor XYZ are$$calendar year taxpayers. In December $20$X$1,$ Vendor XYZ did some work for Business ABC. The vendor provided Business ABC with a bill in December $20$X$1.$ Business ABC did not pay Vendor XYZ$\text{'}$s bill and eventually went bankrupt in late $20$X$2.$

Assume Business XYZ is a Cash basis taxpayer. In what year can XYZ take a bad debt deduction on its tax return due to the loss it took on the bill to ABC?