Pay in advance tax for next year

I’m completing my tax form for rental income and at the end it shows what I owe for last year i paid in advance last year but on the calculation it says zero payment needed for in advance payment for next year why is this when I thought you have to make two payments in advance

Hi,
Payments on account (POAs) are payments made 31 January and 31 July, in advance of the date the tax is payable (31 January the following year). Ideally, both payments on account paid on time, will equal the tax liability calculated by self assessment tax return, so that all the tax is paid in advance of 31 January.  
There are two criteria that must both be met for POAs to be created:
1 - The underpayment of tax is £1000.00 or more and
2 - Less than 80% of the unpaid tax can be collected automatically.  
Payment of tax: payments on account
Thank you.