When to complete a R40 tax form?

Suk1

I was lucky to receive a PPI pay out, on which I have paid £780 tax - I see that you can "earn" £1000 interest before you need to pay tax and therefore it was suggested to me that I could reclaim some if not all of this back. But surely I have paid tax on £3903 interest awarded and therefore cannot claim any thing back? Has anyone any idea? 
£3903 x 20% = £780 

Dazed_and_C0nfused

The £1,000 savings nil rate band is only relevant if you have other income of at least £16,251 (or possibly £17,501) in the current tax year.

If your taxable income is above that level but you are not a higher rate taxpayer then £1,000 of your interest will be taxed at 0%.  Potentially meaning you could get back £200 of the £780 tax paid.

But any other (taxable) interest you receive will be taken into account and that doesn't have tax deducted so if you have say £100 bank interest + £3,903 PPI interest you might only be due £180 refund.

As always some actual facts about your income are needed to provide any certainty

Suk1

Thank you - I do have regular income but below the higher rate bracket - I will complete my tax return and try to claim some of the tax back.