Invoices and Receipts

I was looking back at the previous invoices sent for tax reasons, anyways I was thinking afterwards about the process we follow and wondered if other small businesses follow a similar process.

No matter on what day of the month we have completed our work, we always invoice on the last Friday of every month (provided we are complete) - what date do you choose to invoice or when?

We usually then send receipts out on the last day of the month, no matter what the day is we were paid on - Do you send receipts, if yes on what date or when do you prefer?

Then how do you determine the invoice ref# (we started with 0001)

All of our invoices and receipts are done in excel, nothing fancy but it works. Do you use the same or do you prefer a tool for creating your invoices and receipts?

Is there anything different about your invoice/receipt, i.e. payment stamp on your receipts, thank you notes on both invoices and receipts?

How many times have you received an invoice and you can't make out from head or tail? I have received some of those and I see the importance of clear concise invoices.

I too have paid invoices received, however very few times do I get a receipt...

Quotations

A discussion came about quotations:

The argument was about having your payment/EFT details on the quotation, someone said that they don't agree with having payment/EFT details on the quotation, it is just a quotation. You would only pay the invoice provided, based on the quotation surely?

I personally don't have banking details on my quotations as I don't think that is the right place for it, the only thing I have is the quotation terms.

What do you think about the payment/EFT details on the quotation and what terms do you normally include in your quotations?

I hope the answers given will be useful to others.