Forum Moderators: buckworks
i don't have time to write everything (and i don't know everythng either). i don't know what country you're in, but i'll post this anyway as it'll probably be useful to someone.
in the uk and europe, contracts no longer need to be in hard copy - an online sale is now recognised as a legally binding contract. however, prior to sale you must provide terms etc in a "durable medium", ie, a medium that can be retained by the customer and not modified by the retailer. the uk government stops short of specifying exactly what is and is not a durable medium - they suggest fax and email might be classed as durable, but don't mention web pages. the german government apparently classes web pages as durable.
you can read more about this at the uk DTI site at www.dti.gov.uk and search for "e-commerce directive"
the HM customs and excise say you need to keep VAT invoices for seven years (i think) and that whatever format you provide them in (paper / electronic etc) you must be able to provide duplicate / replacement copies in the future if required. other EU countries will probably have similar rules. i keep all sales records in a database on a web server so i can just run a script to generate a replacement invoice at any time. when i make sales, data is automatically entered into the database and vat invoices are automatically sent to the customer and to me. i also keep copies of all electronic invoices on a separate server just in case of loss of data. i also print all email invoices and put them in folders.
i'm not sure what the inland revenue say about keeping sales receipts etc (and i don't really care because i hate the inland revenue) but i guess the vat invoices i have are sufficient for them.