There is little in the way of guidance for employers about this topic, so we did some digging and came up with this information. We received contradictory answers to our initial enquiries and it wasn't until we spoke to the Case Manager that we received the information we needed.
The Graduated Return to Work Programme is intended to help an employee back into the workplace and you may be requested to supplement their income from ACC by paying the employee a top-up of 20% of their average weekly earnings.
For simplicity we'll use a 40 hour week in these examples, so 20% would represent up to 8 hours of pay. If your employee works irregular hours then remember to restrict the top-up to the difference between what they actually earned and the 20% maximum value.
The top-up is payable regardless of the employee's actual work hours.
If the employee has only worked 4 hours in the week then you need to pay 4 hours and a top-up allowance equivalent to 4 hours pay.
The top-up amount is taxable and is also subject to ACC Premiums (we asked).
When the employee's work exceeds the 20% value (they're managing more hours) then you no longer need to consider a top-up and the weekly ACC038 form will advise ACC that the amount they contribute to the employee can be reduced.
If you have any questions about payments to employees whilst also being paid by ACC then you should contact the Case Manager directly.