Section 465 (d) carryover refers to the at-risk rules of Section 465 of
the Internal Revenue Code. Your losses are limited to the amount you
have "at risk" in the activity. A loss that was disallowed because of
the at-risk rules is generally treated as a deduction from the same
activity in the following tax year (a carryover).
The figure you see
for Section 465 (d) carryover is the amount of loss you weren't able to
take last year and may be able to take this year.
For
more information see IRS Pub.
925 - Passive Activity and At-Risk Rules