Legally required to provide hard-copy of receipts/invoices?

Just a quick question related to my start up.

Am I legally required to provide posted hard-copies of invoices and receipts to clients or are email PDFs sufficient (if I know they can receive and read PDFs)?

Couldn't find anything by searching and I'm based in the UK.

Thanks.

As I understand it, you're not required to send them if the customer doesn't want them. We certainly never have, and our accountants have never complained.

If the customer wants them, then it probably makes sense to send them even if you're not legally required to.

[edit] I'm also in the UK, BTW.

The EU invoicing rules apply to the UK and are quite specific:

http://ec.europa.eu/taxation_customs/taxation/vat/traders/invoicing_rules/index_en.htm

Although I'm in the US, I will say from experience that I tend to keep all my client paperwork virtual (albeit I have extreme backup measures and redundancy) in an easy to access database so I can access requested data on the fly rather than having to dig through archives.

Of course, with company financial documents keeping hard copies is wise, but for routine paperwork - once the project is cleared I archive everything.