Accountant
Transaction locking
Close the books up to a date so nothing can be posted into a filed period.
Lock date
Current state
Nothing is locked. Entries can be posted to any date.
Why this matters more than it looks
Once GSTR-1 is filed for a period, a new backdated invoice makes your books disagree with what the government already has. Locking is the cheapest defence against that. A real system also needs a role that can lift the lock, and a log of who lifted it.