You need to file two tax returns- one Federal Tax Form and another California State income law.My answer to your questions are for Tax Year 2018The limitation date for tax year 15.04.2018Federal Tax return for Individual is Form 1040 . Since you are carrying on proprietorship business, you will need to fill the Schedule C in Form 1040Form 1040 -ES , as the name suggests is for paying estimated tax for the current year. This is not the actual tax return form. Please note that while Form 1040, which is the return form for individuals, relates to the previous year, the estimated tax form (Form 1040-EZ ) calculates taxes for the current year.As far as , the tax return under tax laws of Californa State is concerned, the Schedule CA (540) Form is to be used for filing state income tax return . You use your federal information (forms 1040) to fill out your 540 FormPrashanthttp://irstaxapp.com