It will be pay one time when you take admission in this hostel charge in NIT per sem is about 25k but if your income certificate is less than 2lakh you will get concessions in your fee and hostel fee hope you understand please upvote me thanks for asking this type of question on career 360

Dear Student,

Mess in NITs varies with NITSs. Some NITs there is a regular payment type system i.e. you eat for a month and then pay at the end of the month for what you have eaten. They have a register maintain for all the students and their meals. In others, there is a system like you have already stated in your question. Pay for a full semester and then that is it. In some NITs, there is a cooperative mess. In such a mess, you eat for a semester and then the management will calculate the total expenditure and will ask you to pay the amount which is calculated. In the last case, though they define a certain amount for the semester, chances are that the final figure may vary from the predicted one. If you have paid the fee in advance chances are that you have to pay more and chances are that you will get some amount back. 

Hope this solves your query. 

Thank You.