you need to obtain permission of department before sale of any immovable properties 

The Central Civil Services (Conduct) Rules, 1964

18. MOVABLE, IMMOVABLE AND VALUABLE PROPERTY:

2) 

 No Government servant shall, except with the previous knowledge of the prescribed authority, acquire or dispose of any immovable property by lease, mortgage, purchase, sale, gift or otherwise either in his own name or in the name of any member of his family:

Provided that the previous sanction of the prescribed authority shall be obtained by the Government servant if any such transaction is with a person having official dealings with him.

3) if you fail to disclose sale of property disciplinary action can be taken against you 

Dear Client,

Government servants are required to obtain permission from their department before selling any immovable property. This includes property owned by the government servant themselves, as well as property owned by any member of their family.

If a government servant fails to obtain permission before selling property, they may be subject to disciplinary action. This could include a warning, suspension, or even dismissal from their job.

The reason for this rule is to prevent government servants from using their position to gain an unfair advantage in property transactions. For example, a government servant might be able to buy property at a below-market price if they know that a sale is coming up.

The rule also helps to ensure that government servants are not involved in conflicts of interest. For example, a government servant who is responsible for approving property deals should not be able to sell property themselves.

If you are a government servant and you are considering selling property, you should first contact your department to get permission. This will help to ensure that you are in compliance with the rules and that you avoid any potential disciplinary action.

Here is a more concise version:

Government servants must obtain permission from their department before selling any immovable property. Failure to do so could result in disciplinary action.

18 sub rule 3 (ii)  No Government servant shall, except with the previous knowledge of the prescribed authority, acquire or dispose of any immovable property by lease, mortgage, purchase, sale, gift or otherwise either in his own name or in the name of any member of his family:

Provided that the previous sanction of the prescribed authority shall be obtained by the Government servant if any such transaction is with a person having official dealings with him. 

It is clearly mentioned that while acquire or dispose 

it is advisable to take prior permission and if you will not take they can initiate departmental inquiry against you. 

You are not required permission for making sale but you have to inform the department for sale of property. If you would not inform the department then it would be a misconduct on your party and also violation of service rules. 

Though a government servant needs permission for acquiring an immovable property, he is free to dispose it off without any prior departmental permission, unless your service rules specifically require you to do so. To be on the safer side, seek their permission even if it not required. Otherwise, some adversary in your bureaucracy may bring up the issue later on, especially at the time of your promotion or retirement. Better to err on the right side of caution.  

(1) (i) Every Government servant shall on his first appointment to any service or post submit a return of his assets and liabilities, in such form as may be prescribed by the Government, giving the full particulars regarding - (a) the immovable property inherited by him, or owned or acquired by him or held by him on lease or mortgage, either in his own name or in the name of any member of his family or in the name of any other person; (b) shares, debentures and cash including bank deposits inherited by him or similarly owned, acquired, or held by him; (c) other movable property inherited by him or similarly owned, acquired or held by him; and (d) debts and other liabilities incurred by him directly or indirectly. 

8(ii) Every Government servant belonging to any service or holding any post included in Group 'A' and Group 'B' shall submit an annual return in such form as may be prescribed by the Government in this regard giving full particulars regarding the immovable property inherited by him or owned or acquired by him or held by him on lease or mortgage either in his own name or in the name of any member of his family or in the name of any other person. (2) No Government servant shall, except with the previous knowledge of the prescribed authority, acquire or dispose of any immovable property by lease, mortgage, purchase, sale, gift or otherwise either in his own name or in the name of any member of his family:

Provided that the previous sanction of the prescribed authority shall be obtained by the Government servant if any such transaction is with a person having official dealing with him.

No as you have already taken the same 

- As per Sub-rule (3), of the Central Civil Services (Conduct) Rules,,  all Government servants should give an intimation to the prescribed authority within one month of entering into any transaction of movable property, 

- However, the non-intimation of acquisition of immovable property is only a technical lapse and no major penalty proceeding can be instituted for such lapse.