Abbrevation question, SOC

[vzlion]

I was always under the impression that SOC meant Struck off Charge,
i.e. crashed, burned, unusable etc. Recently, I was comparing some Spitfire serial lists and came across many aircraft that were SOC. In that list they were apparent struck from the squadron roster and transferred to another squadron. Was this a common RAF practice? Or a mis-use of the term SOC in that listing? Was there a special term to indicate transfer from one squadron to another? Thanks, Walt