#AnonymousLegally there should not be a problem in having any designation. Nevertheless, check the provisions of company law in your country
2nd December 2016 From Indonesia, Jakarta
If you are a sole proprietor of your firm you can be a "PROPRIETOR"
If you are a partner in a partnership firm you can be a "PARTNER or MANAGING PARTNER'
If you are a Director and resolved in the board of directors meeting that you have been elected and declared as managing director of the pvt. limited company, you can be a MANAGING DIRECTOR.
In your case you have to be Managing Partner only.
3rd December 2016 From India, Chennai
3rd December 2016 From India, Ahmadabad