Supporting Guidance: employer compliance: guidance by subject: computations: estimating earnings for NICs purposes - posting (allocating) contributions to an employee's NI account
When you have established the earnings (accurately and/or estimated) and calculated any Class 1 NICs due you will then have to consider whether to arrange to post (allocate) the NICs and earnings to the individual’s record.
Arrears must be posted (allocated) where there is a significant impact on the employees’ benefit or pension entitlement.
You do not need to post (allocate) employer only contributions as they are not used to calculate entitlement to contribution based benefits.
In some cases you will have estimated earnings but you will need to ensure you have sufficient information to be able to post (allocate).
Note: Whether or not to post (allocate) is an entirely separate decision to that of whether to estimate. It is based on different criteria.