Pension paid via salary sacrifice

I pay into a work pension via salary sacrifice. I pay tax at 40%. I assume I don't include the amount on my tax return as I've already received the relief. That's understood, but if my pension provider then claims 20% tax relief am I not getting extra relief? Have I misunderstood this? Thanks

Hi ,
 

You're correct - no additional relief would be due on your Salary Sacrifice pension contributions. To clarify what your pension provider is now claiming, please contact them directly. If you require additional confirmation after this, contact us by webchat or phone via : Income Tax: general enquiries   . Thank you .