What are estimated tax payments?
Estimated tax payments are payments for taxes on income that is not subject to withholding tax. This can include income from self-employment, business earnings, interest, rent, dividends and other sources. Many business owners and individuals who receive K-1s for their interests in companies must make estimated tax payments on this type of income. Quarterly estimated tax work is priced at a flat annual rate of $395. Pricing details can be found here.
The IRS requires estimated taxes to be paid quarterly, typically in four installments. If you underpay your estimated taxes, you will have to write a bigger check to the IRS when you file your tax return. If you overpay your estimated tax, you will receive the excess amount as a tax refund (similar to how withholding tax works).