Evaluate your estimated taxes
Estimated tax payments are required if you get income that isn't subject to withholding. It's the IRS' way of ensuring that you're paying as you earn on all your income.
By making the four extra tax payments a year, you'll help ensure you don't underpay your taxes. That's important because if you owe too much at filing time, you could face a tax penalty. But you don't want to overpay your estimated taxes.
Summer's a great time to reassess your estimated tax situation. Look at what you've paid via your April and June 1040-ES filings and see whether your schedule is still on track. If not, you can adjust your upcoming September and January estimated tax payments.