Putting plate on new car

[wellzee]

Hi Guys

Just wondered whether anyone could advise - I'm buying my other half's fathers car off him today. I want to put my private plate on straight away as parking restrictions are ridiculous where I live so could do without two plate changes. Can I send my retention doc with the V5C at the time of change of ownership? It seems so stupid to send that off, wait for a new one, then immediately send it back to change the reg.

Any help greatly appreciated.