As said it's all automated although you do need to declare anything outside the allowances on your SA if you complete one.
A couple of things to be aware of which may be of interest (unavoidable pun!)
If you invest in Fixed Rate Bonds be aware that unless the annual interest is Paid Away eg to your Bank a/c each year, then HMRC will assume that all interest earned across the full length of the Bond period will have been earned on the Bond maturity date - this may tip you into a tax liability situation. Cheeky little scheme by HMRC imo.
Secondly, the number of people I know who do not use all tax allowances available including non-working partners allowances is astonishing. Here:
ISA's are our primary investment vehicle - hopefully the tax-free status will never be removed!
Mrs SD transfers 10% of her Personal Allowance to me.
We use both £1000 Personal Savings allowances.
Mrs SD takes advantage of the £5000 Starting Rate for Savings 'mechanism'. This is often missed by many people. Needless to say, more of our FRB's are in Mrs SD's name than mine.
https://www.gov.uk/apply-tax-free-interest-on-savings