There's lots of info about this online but it really depends on your country. For me, things like my commute to work, expenses for my home office (even though I worked in an actual office until corona), and other things can be deducted. The most ironic category is expenses necessary to file taxes.

Most countries also seem to have savings plans where you put money away until retirement and pay taxes only when you're allowed to take it out, after retirement age (after retirement, you have a lower income, so pay a lower tax rate). Of course, you still pay those taxes (wouldn't be a certainty of life, now, would it?), but they're lower.