Today is the deadline for paying the second installment of your estimated taxes for 2018. Self-employed individuals should include self-employment tax in their payments. High-income taxpayers, whether or not self-employed, may need to pay estimated tax to cover the additional Medicare tax on net investment income. Simplify your payment by transferring funds electronically using EFTPS.gov (www.eftps.gov). It allows you to schedule payments in advance and there’s no government fee for this service.