How do i treat a self assessment payment to hmrc paid from my business account ?

Thanks for visiting the community, @pauline-kirk55. 

If this is a personal expense paid with from your business account,  you can treat a self-assessment payment as personal. This type of transaction isn't considered as business deductible. 

I'd also recommend you speak with your accountant for further assistance. They are the right person who can give you a better advise when it comes to deciding whether to tag this item as business or personal. 

For future reference, you can check out this help article: About SA103F Categories. It'll help you learn about what type of expenses you can and can't deduct. 

Message us again if you have more questions. We're always here to help.