Difference between Execution Date and Rent period

Rahim (Business) (41 Points)

14 September 2022  
Kind advise:

The rent period is from July 2022 for 11 months.
But due to unavoidable reasons, the agreement is made in September .

The firm has received 2 months rent already and GST is deposited accordingly.

So an agreement executed on 1st Sept 2022, mentioning rent period commencing from July 2022 is valid?