@moonlight, thanks for your reply.
Yes, my employer files my return in UK and I get P60.
My query is :
1. For 2016 Tax Return, it was already done by my employer. Halifax statement also says that they rewarded £37.50 (before tax) - £7.5 (tax deducted) = £30.00 (net reward paid).
From the statement, Halifax is actually credited £30.00 (£5 * 6 months) to my account last year and I was not rewarded £37.5 and later not debited £7.5 as it was already done by them. I came to know about this after receiving this letter last week. As I don't do my tax return myself (employer does on my behalf), how do i declare this amount? let me know the procedure please.
2. Secondly, you mentioned from April 2016, bank will not deduct tax. but halifax still credits £5 every month to my account. I presume tax is already deducted every month as the same amount was credited before April, 2016 as well and they might be providing similar statement next year at the same time.
3. As I don't want to risk my ILR, I am OK to cancel this reward or if required, I am ready to return the reward amount to halifax as you know this amount is not making any difference to my finance.
Thanks for your valuable suggestions. Your valuable suggestions are really appreciated.