In this case, 3000 yuan should be given to you, but 900 yuan can't deduct it, and the patent management fee should not be deducted, because the patent is the company's patent. Not only that, if the company implements this invention patent, you can also get 2% of the total after-tax profit. If the company licenses others to use this patent, you should also get the economic benefit of 10% of the license fee after deducting taxes and fees.
If this patent belongs to non-service invention patent, then this patent belongs to you personally. After you apply for a patent, you are the patentee. A company needs the permission of the patentee, that is, you, to implement a patent. In this case, the unit does not need to give you a bonus. You earn as much money as you give.
Judging from what you said, this patent should belong to the former, that is, the patentee is your company. Then, neither 900 yuan nor 600 yuan should be detained. You can find the unit leader to get it back. If the unit refuses, it can try to apply to the Labor Arbitration Commission for arbitration. If the arbitration commission refuses to accept it, it may ask for a notice of rejection, and then directly file a lawsuit in the people's court to safeguard its legitimate rights and interests according to law.