The break down for instrument currency is like this:
To be current (to act as PIC in IMC) you had to do 6 approaches, holding, tracking and intercepting with in the past 6 months.
If you did not do that, you have lost currency; you can not leagally file IFR. To regain currency you have 6 months to do 6 approaches, tracking, and holding. If you lapse that 6 months you need an instrument proficiency check.
Example: You did 2 approaches on 1JAN, another 2 approaches on 1MAR, and another 2 approaches on 1JUL. You want to file IFR on 1AUG; you can not. You only have 4 approaches with in the past 6 calendar months.
Long story short, to file IFR you need the 6 approaches, tracking, and holding with last in 6 months. The addtional 6 months is a buffer for the IPC.
61.57
(c) Instrument experience. Except as provided in paragraph (e) of this section, no person may act as pilot in command under IFR or in weather conditions less than the minimums prescribed for VFR, unless within the preceding 6 calendar months, that person has:
(1) For the purpose of obtaining instrument experience in an aircraft (other than a glider), performed and logged under actual or simulated instrument conditions, either in flight in the appropriate category of aircraft for the instrument privileges sought or in a flight simulator or flight training device that is representative of the aircraft category for the instrument privileges sought—
(i) At least six instrument approaches;
(ii) Holding procedures; and
(iii) Intercepting and tracking courses through the use of navigation systems.