Tier 2 extension salary issue URGENT

[Anitass22]

Hi there,

I am extending my Tier 2 Visa from the same employer for who sponsored me for the initial visa.
Due to economic turns in 2011 my employer had to deduct my salary by 30% on one year which was higher than stated code of practice.

I was told by my employer that they confirmed with UKBA that it was allowed.

1) Could someone please confirm if this is the case and if so what evidence do I need to take with me for the visa extension?
2) Do I need to take the payslip for 3 years?
3) Another issue this creates are the dates my salary was deducted from October 2011 to September 2012 so although the tax paid in 2 years is correct, the gross salary paid differs to the one mentioned on the original COS for 2 years as the dates being between 2 years. is this an issue?

Ironically my visa was granted on 06/04/2011 which seems to be the date major changes came into place.

I would really appreciate if someone could help me.

Regards,
Anita