Grrrr I get a sense of deja vu coming on here - anyway on with the show
If you have any doubts you ideally want to drilldown into last years tax calculation
and click on the tax button
This will fully detail last years info - something along the lines of
unknown (- possibly £1290.24) first payment on acount
unknown (possibly £1290.24) second payment on account
unknown balancing payment possibly £2,739.19
total 2019/20 tax £5,319.67 - this amount looks correct !!
This begs the questions why it would say the following
£5,319.67 balancing payment due jan
Either this figure includes amounts paid and is misleading- or you have not made any payments on account or
If you get the drilldown details from clciking on the tax button mentioned above that should answer the question ref splits above.
Note before you click the "tax" button check how much has been paid towards this bill that will say what you have acctually paid on account (whether payments were due or not) and the total at the bottom should confirm what you still need to pay to clear down 19/20 - if this sum is less than £5,319.67 it looks like the "balacing sum due january" total is faulty. HMRC helpline may be able to claify the confusion.
Also I find how they calculate class 4 NI confusing. Why do they tax me @20% on £16,595 (which is my profit minus personal allowance) but they use a figure of £20,463 to work out my class 4 national insurance, why do they use a different figure and not £16,595.
Thats just how it works
You have £12.5k before you pay tax but only £8,632 before class 4NI kicks in kind os a stealth tax scooping up "tax payments" baddged as "NI" when your income is below the persoanla lowance - both political parties play the stealth tax game
Ref the first and second payemnts on account due these will need to be paid in addition to the unconfirmed other amount. These amounts seem fine based on total tax bill ye 5/4/2020 of 5319.67. In summary have you made no payments on account or is hmrc telling you porkies?