Generally, expense can only be deducted from income. If you have a incorporated business (limited company), and the company has no income, you can not deduct and tax, since your tax will be 0 too. In this case, your income have nothing to do with your company, so deduction is not applicable. So, if you are incoporated and the company has no income, no tax deduction.
If your business is sole proprietorship (not incorporated), your business is you. Your income is your business's income. Suppose you got salary from other jobs, and paid income tax, SOME of income tax can be deducted as business expense or loss.
