National Insurance 0% bands when both Employed and Self-Employed

Hi My question revolves around income tax and NI across both employed PAYE roles and self employed. I left employment in October as a higher rate tax payer. So income tax and NI have been deducted at the prevailing rates. I am now starting self employment. The NI 6% rates for self employment are lower than employee 8% rates whilst employed. I have seen conflicting advice regarding the treatment of the 0% NI band. Question:- If I have already reached the 2% NI band as an employee – i.e. been paid >£50k, is this taken into account when paying Class 4 NI? Or are the two income streams treated in complete isolation? Ie even though I have used a 0% band whilst employed, will the self employment receive a £12,570 0% band, then 6% to £50,270, then 2% thereafter? Or is there no separate 0% band if already used in employment/PAYE? And/or are the two separate streams of income aggregated to determine the total NI? Thank you for your help

Hi,
When your tax return is completed your tax and liability for Classes 1, 2 and 4 NICs will be looked at as a whole and any Class 1 NICs that have been paid will be taken into account when calculating the Class 2 and 4 due.  
However this will only happen if you have registered to pay Class 2 NICs and this is noted on your NI record.  
If you have not done so already, you should register to pay Class 2 NICs as a self employed individual 
Pay voluntary Class 2 National Insurance contributions if you do not pay through Self Assessment
Thank you.