Persefonie

Hello all, I recently sold shares and immediately declared the CGT through the HMRC calculator and the HMRC Real Time CG platform. I am currently waiting for HMRC to approve this but today I chose to sell the last of our ETFs I had on another platform, triggering another CG event. Do I do a submit a new CG return or do I call to correct the one I have just submitted? Apologies for my ignorance regarding terminology, I am simply a nurse trying to do the right thing, not a finance specialist. Kindest