Upfront tax payments

If you have paid an upfront payment in January 2020 for tax year 2019-2020 why does this not come up as deducted when completed tax return and saying that I still owe x amount in which I have paid already. Well most of it anyway.

Hello,

The payments on account that you have already paid will not show when completing the return as this provides an overall amount that is due for that particular year.
Upon submission and processing of your return your statement will then reflect the overall position taking into account what you have paid already.
Regards,