If you are an experienced unqualified teacher with a degree, you can achieve qualified teacher status (QTS) without having to do any further training. Assessment Only allows you to remain in your existing school and demonstrate that you already meet all of the standards for the award of QTS.
This way of achieving QTS is only available to unqualified teachers who have taught in at least two schools. Before you can be accepted onto the route you will need to have satisfied all the usual ITT pre course criteria including passing the professional skills test in literacy and numeracy (until 1st April 2020). Your teaching will be assessed over a period of time in your school by Mersey Boroughs and you will need to present detailed evidence that you meet the standards to achieve QTS.