The act of posting collateral for a loan, does not in itself involve selling the asset. You still own your asset. Sales are generally considered taxable events. For tax advice, please call your tax advisor or the IRS at 1-800-829-1040 or visit their website at http://www.irs.gov/faqs. Although SALT cannot provide legal or tax advice, the IRS recently released guidelines for reporting digital currency activities. You can read the press release on the official IRS.gov website here: http://www.irs.gov/pub/irs-drop/n-14-21.pdf