These allow you to group stock items into categories such as framing, beams, piles, etc under a stock line such as timber. Stock groups aren't necessary for the POS buttons. Unless you wish to set up group level sales specials.
The following example shows the groups of the Carter's 2CG (hardware) stock line.
If you wish to set up sale prices click Edit and check the Sale on box. The form changes to appear as follows:
The sale begins on 11th September, and finishes on the 18th of September. The sale price is retail minus 10 percent. Setting up sales this way means you can define the sale prices ahead of time and carry out the required store organisation prior to the sale starting. With the Sale on box checked the sale will start when the first sale is made of an item in the selected group within the date period defined.
Stock groups are required if you wish to use the Stock lines and groups report. Stock lines only if you wish to use the Stock line only report.
If you intend to organise tax-free sales you need to set up groups. To activate a sales tax holiday uncheck the Sales tax enabled box. If your store deals in things like money transfers make sure the non-stock items used to identify those transactions belong to a stock group with sales tax off.