June 15 was an important day for self-employed real estate professionals: It was the due date for the second estimated tax payment for 2011. If you forgot about it, you can still pay it. The earlier you do so the smaller will be any interest or penalties you'll owe on your late payment.
It's important to remember that self-employed people must pay their income and Social Security and Medicare taxes themselves. Nothing is withheld from their pay. Ordinarily, this is done by making four annual estimated tax payments to the IRS each year as shown in this chart: