Hi BeePee,
I had this done to me because of a PIP backpayment. When I submitted my bank statements, my balance was over £6k at the time, and they requested initially 4 months, but when I told them about this PIP backpayment (without realising that I had a year only in which it wasn't taken into consideration) - they requested a full years worth of bank statements. I had no choice other than to provide them, because they informed me if I didn't, my claim would be closed. It took 13 weeks of them checking back on 12 months of statements, in which they ended up reducing my UC for several months by £100 plus.
Hope this helps with giving you some guidance, but maybe others have experienced different things.
Chris.
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