As a self-employed person, you cannot receive a salary. You can take a draw from your business bank account to cover your personal expenses, but this has no impact on your taxes. You are taxed on your revenue minus expenses; you cannot subtract the draw.
A tax technique for receiving a refund of back taxes by applying a deduction or credit from a current tax year to a prior tax year. For example, a business net operating loss may be carried back for two years.