Yes, if you are filing as married filing jointly and report your businesses on Schedule C or Schedule E, you will just need to file one set of quarterly estimated tax payments. You will want to figure the tax on your combined business income and you will just use your social security numbers on your estimated payments. (Since your self-employment businesses are considered disregarded entities and are being reported on your jointly filed income tax return.) The IRS will not need for you to distinguish between the 2 separate business when filing your estimated tax payments.
