Difference between43b and 40a(7)

As per sec 40 A(7) deduction for gratuity is available for employer only when it either become payable in the previous year or provision for that as a contribution to approved gratuity fund has been made.

but This applies sub. to condition u/s 43 B

which says that it will be allowed as deduction when the actual payment has been made either in the previous year or can be claimed on due basis provided the payment (for the provision of previous year) has been made before the date of filing return u/s 139(1) 

hi sir please explain with example and also what is tratment in form 3cd and Financial statments and in computation of total income