If your parents sold their primary residence they are able to exclude up to $500,000 in capital gains from the sale. To qualify as their primary home they would have to have lived in the home for a period of 24 months in the 5 years before the sale date.
Form 1099-S is an informational form that has information that may or may not have to be reported on a tax return. If would appear that the gross sale amount was less than $500,000, therefore, the closing company issued a 1099-S with no amount reported on Form 1099-S. If this is the case then you do not include Form 1099-S on the tax return.
**Say "Thanks" by clicking the thumb icon in a post
**Mark the post that answers your question by clicking on "Mark as Best Answer"