File incomplete or Late P35 ??

I have a client, recently taken over, who has used a now defunct bureau service to prepare payroll for his employees (approx 100 in construction industry)

The data is available but will not be available until tomorrow/next week so we are left with two choices;

• Delay, get the return right and face the £100 penalty - as long as in during the next week we are assuming this minor issue will not affect gross CIS status
• Submit a part complete return now and then an amended one next week (not my preferred option)

Could someone advise if the first option would be the way forward - it is my choice but a second opinion would be very welcome

Thankyou.