If you make £13 a year living in United Kingdom, you will be taxed 0. That means that your net pay will be £13 per year, or £1.08 per month. Your average tax rate is 0.0% and your marginal tax rate is 0.0%. This marginal tax rate means that your immediate additional income will be taxed at this rate. For instance, an increase of £100 in your salary will be taxed £0, hence, your net pay will only increase by £100.
A £1,000 bonus will generate an extra £1,000 of net incomes. A £5,000 bonus will generate an extra £5,000 of net incomes.
NOTE* Withholding is calculated based on the tables of United Kingdom, income tax. For simplification purposes some variables (such as marital status and others) have been assumed. This document does not represent legal authority and shall be used for approximation purposes only.