When to pay CGT

Good Morning, I sent my CGT calculation to HMRC approx 2 weeks ago. I cannot see anywhere acknowledgement that they have received it and my accounts states i've nothing to pay, although i know there is an amount payable. Does it take time to show on account or have they not received my form? Thanks

Hi,
Please find guidance: Report and pay your Capital Gains Tax 
For information there is also:
Check when you can expect a reply from HMRC 
Thank you.