Yes, you were legally terminated as an "at will" employee.
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Concurring with Mr. Leroi -- please remember that Colorado is an "at will" employment state which means that unless you have a written employment contract for a term or some sort of writing that can reasonably be interpreted to reflect that your employment relationship is something other than "at will" the relationship may be terminated by either party, with or without cause, with or without notice, for any reason or no reason at all. That said, it does seem that the compensation 'structure' of your arrangement and the comment concerning salary and the employer not 'liking' overtime may be a potential issue in that the Fair Labor Standards Act outlines the terms under which employees may be classified as Exempt versus Non Exempt (OT eligible). Yours does not sound to me (without knowing enough to advise) like an Exempt (i.e. salaried) position. So, I suspect that your employer may not be acting in proper accordance with the dictates of the FLSA. However, the ultimate question -- for you -- will one of damages which is to say that even assuming that you were improperly classified and terminated (with or without cause, properly) how many hours did you work beyond 40 in the time that ou were there?
To the extent that you believe you have an action worth pursuing you can certainly send a letter directly to your former employer, you can call the CO DOL directly and discuss the situation with them. You can certainly reach out to any number of attorneys as well.
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