HMRC may ask you to send your bank details to receive a refund from them. HMRC will expect you to send this through an EPS.
Bank Account EPS
Quickly create a bank account EPS by going to HMRC -> RTI Submissions. Click the +Create button in the top right hand corner and you'll see Bank Account EPS is available.
You then get a box to enter your bank details.
You'll then get an EPS that you can submit to HMRC.