I have a client sold his rental property back in 12/8/18 and then bought another property to complete the kind like exchange process on 4/26/19 to the new property.  The property contain him and his girlfriend's name on it.  His girlfriend doesn't have any source of income and still in school.  In this case, is his girlfriend required to complete her own tax return with 8824 form attached on it or is it ok to file 8824 on my client's tax return only since his girlfriend is listed as a dependent on his tax return?

Also I want to confirm the 8824 form is only required to file when the exchange process completed on 4/26/19, meaning he won't need to file a 8824 form in 2018?

Thank You