Hi Andycharger,
Most shops would expect some form of credit in my view so this is a wise choice, how much you give them is totally up to you and what suits your business, no legal requirement. 30 days is a fairly good UK standard, although 7 or 15 days is also common. Depending on how much you invoice, you may want to think about if it's termed from invoice date or from month of invoice. If you invoice a customer a number of invoices a month and these are consolidated to due by month of invoice it means you should expect one payment a month rather than a number of smaller payments through the month. (But that depends on how cash rich your business is and obviously how it fits with you). Also consider additional discount for early settlement within the terms if you want to reduce risk and speed up cash flow?
For documentation:-
We have the agreement written up and an application form for a credit account with us. The form will cover the basic information needed for credit checking, including directors, address, contact information etc etc. Also it covers agreement our terms and conditions such as ownership of goods, any interest charges we may charge if payment is not received within agreed terms and much more. This could also be covered off when you discuss the sale etc, always get a signed agreement in place, not just for agreement to credit terms and payment, but also any other T and C's you may want to impose. That way if you if anything does go bad you have a better starting point for legal/ administrators. Also worth ensuring you have a retention of title clause in your T and C's. Depending on the clause written, it would mean you ensure ownership of the products either outstanding (invoice not paid) or sold to them (on invoices paid).
Credit checking is very wise, many companies offer a service and they vary a great deal in terms of price and quality, but the service they provide is invaluable in trying to avoid bad debt. Shop around before agreeing to sign up. A lot of place do free trials as well so you can check they are suitable for your business. You'll probably use it more of a guidance than a definitive answer, there is an element of gamble when giving credit to any customer and these agencies are usually conservative in their suggestions. They certainly do give a good starting point though- Also in addition to this, if you know how to read balance sheets and profit and loss you can get these from companies house for £1-£2 and can also give you some additional comfort.
Finally, make sure you have a good sales ledger record of invoices outstanding and a credit control process in place to handle these. If you've one or two invoices a month/ week this should be something fairly easy to manage, but as you grow you need to think about proper administration of this, either additional resource internally, or other services like factoring, or outsourcing.
Hope that helps to get you started and feel free to drop me any PM's if you need more help and guidance. I'm new to here as I'm just forming an outsourcing collections business- so this is within my specialist field, and I'll be happy to advise as best I can.
Thanks
Carl