The sum of estimated payments must equal at least 85% of estimated tax liability for the year, and the amount of each estimated payment must reasonably approximate the tax liability for that quarter. For Tax Year 2009 and after, if prior year's tax is $20,000 or less, estimated tax may be based in the prior year's amount in four equal payments, the sum of which equals the previous year's tax liability. If the year's tax liability is $800 or less, quarterly returns are not required.