Question regarding salary

[broccoli]

I'm wondering as to the procedure to follow in case the employee is to receive a small salary raise. Particularly:
- The CoS states that employee is to be remunerated £x. That figure is going to increase (by a small factor) due to a performance review. Is that a problem if the employee recently joined using that CoS?
- Who needs to be informed? UKBA? Is there a rule that states that raises up to £y amount are fine and do not require any changes to the sponsorship?

Thank you

[manci]

the employer has to report to UKBA:
a change of salary from the level stated on the migrant’s CoS, other than changes due to annual increments, bonuses ........
(tier 2 sponsor guidance, paragraph 548)