New Jersey business owners often need to pay quarterly estimated taxes to avoid penalties and underpayment interest. NJ quarterly estimated taxes are advance payments of state income tax required when your income isn't subject to withholding. Self-employed individuals, freelancers, and business owners expecting to owe $400 or more in NJ taxes must make quarterly payments to avoid underpayment penalties. Who Must Pay NJ Estimated Taxes? You must make NJ estimated tax payments