Strange "balancing payment"

leo.ge

Hello!
I just started being self employed last year, so I am applying for my first tax return. I filled all online forms (for 2017/18) and my total income is 14,620. It shows the following values:
Personal allowance £11,500
Total income on which tax is due £3120
Income tax £624
NI £720.69
Total £1344.69

And then it shows:
Balancing payment: £602.52 and then it shows the total I need to pay is £1344.69 + £602.52 = £1947.21.

Why is this and why should I pay these additional £602.52?

(By the way, some online calculator shows I even need to pay even less: total of £1296, which is £650, so I am totally confused).

(I am 18 years old and study in university, not married, don't have children etc.)

Icequeen99

Yes, you have to pay the tax due for the last tax year plus a payment on account for the next tax year which is calculated as 50% of your tax bill.

It is explained here: https://www.gov.uk/understand-self-assessment-bill/payments-on-account

It means you will have less to pay next year.

IQ

pramsay13

Once your tax owed is over a certain amount you have to pay it in 2 installments and up front, so they are looking for all of 2017/2018 tax plus 50% of 2018/2019 tax. They are assuming this will be the same amount although when you do your tax return next year this will be adjusted.
You will owe the other 50% by July 2019 and assuming nothing else changes you will keep paying the 50% installments in January and July.

Dazed_and_confused

But don't think of it as "up front".

By the time you make the first payment on account for the 2018:19 tax year on 31 January 2019 you will be there quarters of the way through that tax year. People on PAYE will have been paying tax each month since April on income received in 2018:19.

leo.ge

Many thanks, now I understand!