Tax credit - notice to pay

[StringTheory]

In August 2015 my circumstances changed which meant we were no longer entitled to Tax credits and we received a letter to say to say we were over payed by £300. Since then I have received nothing else. I am waiting to be contacted by the HMRC with instructions on how to pay them back and when. I'm finding it hard to find useful information online but can see it's called a 'notice to pay'. Does anyone know when I should be expecting this? I don't really want to have to call them again as I spent what felt like hours on the phone to them last summer trying to deal with what felt like an incompetent call centre.

Thanks

The overpayment of £300 will be an estimate
They won't be able to confirm the exact sum until the tax year ends in a few days time
I would expect them to send you an annual declaration form where you declare your income figures for April 2015- April 2016
Then following that you should get details of how to repay
You might not get the declaration form until late May

Ah ok, great. Thank you for your response. I wondered if they were waiting for the end of the tax year.