Instrument rating in the United States

An instrument rating is required for a pilot to fly under instrument flight rules (IFR). In the United States, the rating is issued by the Federal Aviation Administration.
Instrument rating standards.
To be eligible to pursue an Instrument Rating, the applicant must:
Operations requiring an instrument rating.
A pilot must have an instrument rating in order to act as Pilot in Command of a flight below VFR weather minimums and/or under IFR. The rating is also required:
IFR currency requirement.
Under FAR 61.57, to be eligible to fly in Instrument Meteorological Conditions (IMC) an IFR-rated pilot must accomplish and log at least the following IFR procedures under actual or simulated IMC every 6 months:
An Instrument Proficiency Check administered by a CFII, DPE or ASI within the last 6 months is another way of complying with the IFR currency requirement.