how to calculate tax on self employed + employment income

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hi,

basically i need advise on tax, i am in full time employment and my current salary is £26k, last week i applied for my visa extension and i was short of 5k which i covered through self-employment, my net earnings after expenses through Self-employment were £5200.
now how much tax i need to pay on this 5.2k and how do i pay, whats the deadline to pay that tax. is there any website who calculates the tax.?

many thanks