Voucher & Discounts.

v_code	is the code you pass on to your customers.
v_rate	Is a percentage discount from the total price (excluding P&P) (Or use v_amount)
v_amount	a fixed amount discount. (Or use v_rate)
v_usage	1 = individual; 2 = multiple. Indiviual means it can only be used once, such as a one of gift certifacte, 2 means it can be used many times.
country_id	If you want to limit the discount to a particilar country.
postage_zone	" " " postage zone
valid_from	Date in format YYYY-MM-DD
expiry_date	Date in format YYYY-MM-DD
minimum_order	If customer has to sepnd a certain amount (before p&p) to quality enter amount here.
valid	1 is valid, 0 turns the voucher off (in case of fraud)
v_method	1 - Discount. 2 - No discount: perhaps a free gift or to charity.
Comments

database.vouchers_tbl
+---------------+-----------------------+------+-----+---------+----------------+
| Field         | Type                  | Null | Key | Default | Extra          |
+---------------+-----------------------+------+-----+---------+----------------+
| id            | int(10) unsigned      |      | PRI | NULL    | auto_increment |
| v_code        | char(32)              |      |     |         |                |
| v_rate        | decimal(8,2) unsigned | YES  |     | 0.00    |                |
| v_amount      | decimal(8,2) unsigned | YES  |     | 0.00    |                |
| v_usage       | tinyint(3) unsigned   | YES  |     | 0       |                |
| country_id    | int(10) unsigned      | YES  |     | 0       |                |
| postage_zone  | tinyint(3) unsigned   | YES  |     | 0       |                |
| valid_from    | datetime              | YES  |     | NULL    |                |
| expiry_date   | datetime              | YES  |     | NULL    |                |
| minimum_order | decimal(8,2) unsigned | YES  |     | 0.00    |                |
| valid         | tinyint(3) unsigned   | YES  |     | 1       |                |
| v_method      | tinyint(3) unsigned   | YES  |     | 1       |                |
| comments      | char(255)             | YES  |     | NULL    |                |
+---------------+-----------------------+------+-----+---------+----------------+