Do I have to insure and bill a domestic helper even for a one-off assignment?

No, you do not have to register your domestic help for a one-off assignment. As far as insurance is concerned, there are two points you should consider:

1. Your domestic help works on a self-employed basis and bills you. In this case, the domestic help is self-insured.
2. The cleaner is paid on a marginal employment basis via a service cheque. Accident insurance is already included in the service cheque. There are no further costs for you.