Payments on Account

The current year online Self Assessment calculation doesnt appear to allow for the 2 payments on account required by the previous year's Self Assessment when showing tax that is due. Will the online system provide an updated amount on tax due for the year after a couple of days when various HMRC systems have reconciled OR do I determine and make an manual adjustment by deducting the 2 Payments on Account from the amount of tax due for current year and make that payment? Is the total credit balance available on line? I have looked but cant find it so if instructions would be welcomed. Finally can I make the final payment of the year and the 1st installments in separate payments?

Hi
Once you submit the return, the statement will update to take into account the payments you have made direct and a revised balancing payment, if applicable, will show.