Tax treatment for a lost deposit in an insolvent financial institution is covered under Section 165 losses. Basically, you need patience to wait for a court to rule it's a "sustained loss" after all recovery efforts and that loss write off can take over a year.
We have content about Section 165 losses in our Trader Tax Center (recapped below) and our blog, where we covered the MF Global and PFG insolvencies. MF Global was Section 165, but PFG was different: it was deemed a theft loss which allowed more generous tax treatment known as the Ponzi ruling. That revenue procedure allows faster write offs with ordinary loss treatment. Otherwise, Section 165 is capital loss treatment, unless you had trader tax status.
If you got caught on the wrong side of the forex trade with the SNB announcement, and your forex broker liquidated your forex positions due to market losses and lack of margin, that's a forex loss, not a deposit loss. If you use the default Section 988 treatment, it's an ordinary loss, but not a business loss without trader tax status, so you need other income to absorb the loss. If you filed a Section 988 capital gains election, it's a capital loss. If you're using Section 1256(g), you can file a Section 1256 loss carry back election for 2015 to carry the loss back three-years to offset Section 1256 gains.
Deposit losses (in our Trader Tax Center)
Many investors, traders and hedge funds got sideswiped by the MF Global and PFG bankruptcies over the past few years. Unfortunately, futures and forex account holders are not afforded government protection like bank account holders with FDIC protection and securities account holders with SIPIC protection. Tax treatment is far better when the IRS declares the loss a “theft loss” and allows application of IRS Revenue Procedure 2009-20, originally enacted to provide tax relief for investors in the Bernie Madoff Ponzi scheme. Theft losses receive ordinary loss treatment plus acceleration of losses on tax returns. Otherwise, Section 165 applies to deposit losses in insolvent financial institutions like MF Global. Investors are stuck choosing between capital loss treatment, which may trigger capital loss limitations, or itemized deduction treatment with various restrictions and haircuts. Business traders with trader tax status benefit from business ordinary loss treatment. Taxpayers with Section 165 losses must wait for the loss to be “sustained” so trustees have ample time for fund recovery. MF Global futures account holders recovered their losses in full, although forex account holders may have some sustained losses. (Read our
blogs,
PFG investors can deduct theft losses on 2012 tax returns with Rev. Proc. 2009-20 safe harbor relief, and
MF Global & PFG Best deposit losses have nuanced tax treatment.)