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The $3,000 loss must be included on Form 1040 line 7, but whatever portion of that $3,000 doesn't reduce your taxable income gets added back to your carryover to next year on the Capital Loss Carryover Worksheet.  If without including the $3,000 loss on line 7 your taxable income on Form 1040 line 15 is above zero, your carryover is still reduced by the amount of the loss that should have been used.