I think I have been able to correct my issue after reading another post answered by Sam_R on this post: STP Phase 2 Payroll Tax Reporting )
I checked to see whether each of the categories showing as "not assigned" were set up as taxable or non-taxable.
As per Sam_R instructions.... "To check this, please navigate to the 'Setup' dropdown > 'General payroll information' > 'Set up Payroll Tax' > please check here if the category in question has a 'tick' next to it or not. If the category isn't ticked, this means you do not wish tax to calculate on it, hence - not reflecting on the Payroll Tax report. "
After ticking my 4 categories showing on the report as "Not assigned" they have now moved back up with all the other Wages categories.
I guess the next thing I'm going to have to worry about is whether I now have to sort out something to do with tax. I'm thinking since the tax year has passed it is possibly too late.
