Quickbooks Pro, the preeminent bookkeeping software for small businesses is free today at Staples store across the U.S. after a mail-in rebate. Normally $199, you can buy it at the store for $40 off and then send in a rebate for the rest of the $159. This deal is only available today, December 22, 2008.

Quickbooks Pro 2009 by Intuit
Quickbooks Pro 2009 by Intuit

The deal is also supposed to be available online, though at least one Lifehacker reader claimed that the website was out of stock.

This is likely a move to try to get people into Staples stores before the Christmas holiday. Intuit, the makers of Quickbooks, could have allowed a one-day download of the product and avoided the entire rebate process and the adminstrative work that goes into pulling of a rebate operation with a download process. Still, the software is free, so if you’re not stuck in the terrible weather hitting much of the country now (like the Pacific Northwest), you may want to try to get over to Staples before the end of the day.

Don’t know what Quickbooks is? Many small businesses use Quickbooks to keep track of their business’ finances, “from entering sales receipts, tracking expenses, preparing and selling invoices, sales tax tracking and payment, preparation of basic financial statements and reports, and inventory management,” as Wikipedia puts it.

Quickbooks is so popular in part because it does not require users to understand the principles of accounting and is relatively user friendly for most use cases. Receipt management service Shoeboxed will begin to integrate with Quickbooks services in the near future.