1) The application charge for any land conversion petition shall be Rs. 10, irrespective of the quantum and Category of land. 

2) The applicants can approach the Office of the concerned Block Land and Land Reforms Officer at the Panchayat Samiti level or in the Office of District Magistrate of the relevant block or district.

3) You can also download the application form for the land conversion from the official website of Land Reforms and Refugee Relief and Rehabilitation Department, Government of West Bengal

4) 

The following documents must be furnished while applying for land conversion in the State of West Bengal:

• Mutation Certificate.
• Application in Form 1A.
• Copy of current R-o-R (in the form of a Khatian or Parcha).
• Copy of current Rent Receipt.
• Sketch map showing the approach road.
• Plot Information with or without a map.
• Copy of NOC of Pollution Control Board.
• Copy of Detailed Project Report (DPR).
• Certificate for setting up of Industries by Industries Centre / DoI / Department of Commerce & Industry, Government of India.
• Any other documents as required by the Collector.

the meaning of “Danga or Bastu (or Vastu land)” Shali in West Bengal ? ... Literally Danga is an non agricultural high land. It is the land just beside a Pond. For constructing house, the nature must be converted from Danga to Bastu ( or Vastu).

You may contact a lawyer in the local who practices in service law for further advises and suggestions to move on.

Government cannot vest any land unless there is provision for proper compensation in the West Bengal Land Reforms Act.

1. It shall have to find out as to when was the said land declared as vested on which your house has been constructed.

2. You shall have to apply for getting your said land released from being vested..

3. It is a time taking job and there is expected to be some Misc. expenses amount of which can not be foretold before conducting investigation in to the matter.

You need to find out an advocate in your district to file a case for conversion of land use. The land will be converted for residential purpose by the court and mutated by tahsildar after order from the court. 

1. Your father have to apply for conversion of land to Non vested land.

2. The application should be made before district collector for change of land status.

3. Fees for conversion will be according to value of property.

You need to apply to convert the same into non agricultural in BL and LRO office in your jurisdiction and pay applicable fees 

An application must be given in the tehsildar office to convert the property into non agricultural land and it would take a few months. Effectively pursue the case so that it is done expeditiously.