Quotations, Invoices, credit notes, Goods received vouchers, Purchase Orders
How should these be stored within a database?
My thought was to have a table that contains all the general information for all these documents i.e.

Document_Number
Document_Type i.e. 1=Invoice, 2=Credit Note, 3=Goods Received Voucher etc.
Accounts code
Account Name
Address
Document date
Order Number
Etc. etc.

A second Table would contain All the Document Lines i.e.

Document _Number – (Ties up with The Table as above)
Document_Type (as above [Invoice, Credit Note, GRV etc])
Quantity – (This may be positive or negative depending upon the type of document)
Product Code
Product Description
Price
Discount %
VAT / Tax Rate
Etc. etc

Is this the correct way of doing this or should each document type have its own main table and each document type have its own document lines table?????
My concern with using a single table for each is that the table would be fairly large after a period of time yet look up would be really simple?