Some specific situations when one shares his or her nanny...

What are the cases that can cause parents to review the administrative side of their shared custody agreement?
It's the withdrawal of one of the parents which  usually requires finding a new family to continue the shared childcare. It might also happen that one of the families needs more hours of care than the other.

Special situation: you're going to share your neighbour's nanny

The big advantage in this context is that you'll get to skip the many stages of looking for a nanny.
If the nanny has already been working for the family for several months, she has certainly proved herself. They probably wouldn't offer shared childcare if things weren't going well.

Normal care + shared care

If the children of both families are cared for during the same hours, then the contracts will be "shared childcare".
If one of the two families uses the nanny for additional hours outside the shared childcare schedule, it must be clearly stated in the contract when it is shared childcare and when it is "private care". The payslip will include the total hours of the two types of arrangements.
Of course, hours of private care are only paid by the family concerned. Overtime calculation must take into account including hours of both types of care (above 40 hours per week).
To be noted on the contract: