Two boxes matter on Form 8949: Box H: short-term gains (assets held 365 days or fewer) Box K: long-term gains (assets held 366 days or more) Wrong box = IRS mismatch flag. Not because you did something wrong, but because their system is checking that your holding periods are classified correctly. Your crypto tax software should handle this automatically based on purchase dates, but it's worth verifying before you file, especially if you have positions you held across the one-year threshold.