If you are UK non-resident you may still be able to get a personal allowance in certain situations.
Your personal allowance is the amount of income you can earn before you pay tax. The current level of personal allowance is £12,570 for 2021/22 ( and £12,570 for 2022/23). If you are tax resident in the UK you will normally get a personal allowance. If not, you might still be able to get a personal allowance in some circumstances, for instance if you are a citizen of an EEA country. If you are non-resident, you might also be able to claim the personal allowance if there is a double taxation agreement between the UK and the country you live in.