If the certificate credit rate shown on line 2 is more than 20%, multiply line 1 by line 2, but do not enter more than $2,000 on line 3. If you and someone else (other than your spouse if filing jointly) held an interest in the home, the $2,000 limit must be allocated to each owner in proportion to the interest held. See Dividing the Credit in Pub. 530 for an example of how to make the allocation.