Tax on Savings Interest, and Dividend payments vs. allowances.

I have 2 questions regarding savings (interest) and investments (dividend) income. 1 Savings interest I believe that the first £1000 of savings interest is tax free in a given tax year. And if income is less than £17570, that allowance grows to £5000. I also believe that for someone earning more than £17570, but is still within the basic tax rate range, earning less than £50,270, if interest income is over £10000 then self assessment is needed. However, I am unclear what happens for savings interest between those levels i.e. £1001 to £10000, for someone with income greater than £17570. I've seen some discussion here suggesting that interest in this area is shared by the financial institution with HMRC, who will make any necessary adjustments, and no action is required by the individual. Apologies if this has been answered previously, but I wanted to make the enquiry based on current processes. Can this be clarified please? 2 Investment dividends Reviewing historical dividends and changing allowance levels, if that dividend was actually slightly over the allowance, what is the best way to resolve that? In light of allowance levels changing in the future I'd like to understand that process better to address matters in a timely manner. Thankyou

Hi Star Gazer,
1. UK banks/building socities notify HMRC of interest paid so if your total intertest from these sources is less than £10,000 you do not need a tax return.
Do not include any interest paid from an ISA in these figures. if your interest is from any other source, you would need to advise in writing and provide evidence.  
2. As we are not notified of dividends, you will need to also advise of the correct figures yourself. this can be done in writing or by telephone as no tax is deducted at source on these.
Thank you.