The title is somewhat misleading. Under the current PAYE system, the employer gathers the tax information on behalf of the employee and files it with the HMRC

The title is somewhat misleading. Under the current PAYE system, the employer gathers the tax information on behalf of the employee and files it with the HMRC at the tax year end. Under the proposed new system, details of the payment are sent to HMRC electronically on each paycheck. Which makes sense when you consider that most payrolls are electronic. The idea is that this will reduce bureaucracy and also makes it easier for contractors and for people who switch jobs a lot (and the companies that employ them). If your company doesn't have a compatible electronic payroll system then you would still be able to file at the year end as you can now, except it would be an online-only filing with no paper forms.