If someone has two income streams. Main through an employer and a self employed income streams. Can they take standard deduction for their income through employer but also file itemized deduction for self employed income? Or does the deduction have to be same for both?
Assuming you're in the US, not as you describe. What you do is file a Schedule C for the self-employment income, where you can deduct business-related expenses. The result then is entered on your 1040 (line 12, I believe), and added to all your income from other sources to give your total income. Then further on in the form you can choose whether to take standard or itemized deductions on that total. But you can't deduct the same thing twice, though you can e.g. split mortage interest expense into business and personal parts if you're using part of your home for business.