Is it right to block a good customer if he/she delays paying the due once on time? What should be done instead?

Good customers have bad days too. I believe that all customer oriented businesses should adapt a system to accommodate these bad days and to ensure we pass the message loud and clear to our customers that we trust them and we will make room to accommodate them during their moments of difficulty.

In return, this would create a feel of loyalty between business and client and would pave the path for a stronger relationship.

No Its not a good idea to block a good customer, You will be loosing him or her forever for this. It's Better to give him/her time once or twice & by that time we should go on with our continuous follow ups. 

Its is not a good decision to block good customer instead it should be followed properly time to time till we get the paymeny and we should consider that its not easy to make customer. 

This is the Company's discretion, if the customer has a good track record, some companies are extending the due as a courtesy, while others stick to the contract the customer agreed upon. If you are faced to such dilemma, ask for permission of the higher up. 

No, it is not a good practice and customers are the king of the business.

This is one of the tough situations in business to maintain a positive relation with a customer/client but also receive payment for services provided. For late paying clients I have found that a late payment penalty is a good motivator. Another thing to check with the client and see if they have specific cut off dates for their payment cycles - you may be falling into period where you roll into the next payment cycle. One thing that has helped is to have clients on electronic billing and payment transfer. They tend to pay quicker.  You can also address up front with the client and assign payments to milestones in the project - if you are providing consulting services. A payment is required at each milestone gate and then you proceed to the next phase after payment is received. This helps motivate the client so that they get their end product. 

If a customer delays paying the due, he/she dont have consideration to the work i have made and  time dispendended with him. We must wait the due payment

No.As what they say that customers/clients are the ling of the business, we should be considerate to them,coz we dont know the reasons of their delays.Follow-up their payments and maybe additional penalties instead of blocking them.