Timing of PPI payment question

Suzy_P

Hi, I hope someone can help me.
In 2016/17 I was a 20% tax payer, with untaxed savings interest allowance of £1000. In 2017/18 I became a 40% payer, with untaxed savings interest allowance of £500, which I believe is relevant for these payouts.
In March 2017 I was offered a payout on mortgage PPI, which deducted £331 tax. I accepted in writing the following day, but the payment wasn't made until 12 April 2017. (Of the year in which I later breached the higher tax rate band).  As I had savings and a bank account paying interest, I ended the year 2017/18 having earned interest almost  to the £500 limit.  
What I want to know is whether the tax is due as at the date the offer is made/accepted, or the date the payment is made?  If the former, I can reclaim it, otherwise, I have lost it 
Thank you for any advice.

[Deleted User]

It's when payment is made - ie when you received the income.

Suzy_P

Thanks zx81, I was afraid that was going to be the answer. Annoyed they took a month to process it though!