If you sold your primary personal residence and you lived in and owned the home for at least two years in the five year period on the date of sale, you do not have to report the sale if your gains are less then the exclusion amounts of $250,000 if filing Single or $500,000 if filing Married Filing Jointly (and both lived in the home for two years).

If you had a gain greater then the exclusion amounts then you would have to report the sale. Also, if you received a Form 1099-S for the sale either with a gain or a loss, the sale has to be reported.

Gain or Loss equals Sales Price minus Sales Expenses minus Adjusted Basis (Purchase price plus the cost of any improvements prior to sale)

Just so you know---or so that others reading this thread will know----investing your profit into buying another home has no relevance.  The law that allowed you to avoid capital gains tax on the sale of a home if you purchased another home with the gain was changed in 1997.