Property held jointly by married couples or civil partners: Form 17 rule - strict time limit
The declaration must be given to the Inspector within 60 days of the date of the declaration.
The declaration time limit of 60 days must be enforced strictly. There is no power to extend it. Since difficulties might arise only many years later - perhaps when the couple split up - you must make sure the notice of declaration is valid at the outset. TSEM9874 tells you what to do if the couple say a notice has been sent but you cannot trace it.