Not charged enough for postage

[debbikubien_0]

I’ve just sold an item and received payment but then realised I hadn’t charged enough postage.  Does anyone know how to claim the additional cost from the buyer who is happy to pay the extra.  There doesn’t appear to be an option to send an invoice now that I’ve been paid.  Advice welcome, thanks

[plpmr]

adding to the advice already given -

Obtaining any payment outside the eBay transaction is a serious breach of eBay policy.