NI Back loaded

HI There,

I am set up on our Payroll as a director that takes a salary each month which is just under the tax threshold.

For 9 months of the year the system didnt make and NIC's and then for the last 3 months has taken £126.50.

Is the system supposed to do this as it doesnt seem right, surely it should spread the payments over the year.

Advice.

Thanks

Kevin