Hi N S Juty,
If your return calculated an overpayment, this overpayment will have been added to your statement.
This overpayment will then have been applied against your 2nd Payment On Account , after which the remainder should be claimable as a credit.
To allow us to confirm this, we would need to review your statement.
Please contact us by webchat or phone here to allow us to do this:
Self Assessment: general enquiries
Thank you.