will I have to provide banking information and tax forms upon enabling IAP in addition to signing the Paid Applications agreement? Here https://help.apple.com/app-store-connect/#/devb6df5ee51
it says 
To sell your apps for a price or offer in-app purchases, the Account Holder user must sign your Paid Applications agreement. 
To receive payments from Apple, you will also need to set up contacts, enter banking information, and submit tax forms. 

My question is will I have to provide banking information and tax forms upon enabling IAP in addition to signing the Paid Applications agreement?
Or will they be required only when trying to receive payments?
You have to be set up for billing and taxes in one country to put an app on the store, free, paid or some mix of both. 

You don’t have to execute tax documents internationally until you put an app as available in those regions, but you do have to fill out the basic forms to push your first app through the pipeline that ends up on the store.