I think it would be good if when you make a call to companies house to fetch the company details if you can also make a call to a VAT API to check if the company has a VAT number and if it does autofill it on the client creation page.
Happy to look into this, do you have any recommendations for a public API that can return VAT numbers? I don’t believe HMRC have any publicly accessible data-sets on this.
I know you can use VIES but that’s for identifying companies from a VAT number and member state.
I did have a look before I made this post however I came up with the same as you.
There’s lots of vat number lookups to gets company but not many that do the opposite.
I will have a proper look round and repost back if I find something.