There are three circumstances in which you are legally obligated to disclose your disability:

• You are in need of accommodation in the workplace. You can disclose during the interview, at any other time in relation to your employment, or at any time during the process of applying for employment 
• It is likely to affect your work performance, attendance, or your ability to fulfill the essentials duties of your job. As a general principle, if you choose not to disclose your disability, it is important that you be able to complete all the essential duties of the job before accepting it.
• There are health or safety risks for yourself or your co-workers.

If your circumstance does not apply to any of the three cases listed above, you can choose whether you would like to disclose your disability or not, depending on the situation and your comfort level.