Bill of Materials (BOM) in Sage is designed to handle sales and inventory where you track both an end product you sell and the subcomponents that make it up. Click here for Sage's full knowledgebase article on BOMs.
The Bill of materials tab in the Sage product record for the end product holds the details of which subcomponents are used, and how many of each. BOM is only available in Sage 50 Accounts Plus or Sage 50 Accounts Pro.
With BOMs you're required to have one Sage product record for every end product you sell (what your customer actually buys) and also one for each subcomponent you wish to track inventory of. This does mean if e.g. I give customers the option to buy batteries in packs of anywhere from 1-100 and I also want to track inventory of those, I need 100 product records in Sage to reflect this.
BOMs can be comprised of multiple different items - e.g. I sell tables (end product) by buying in tabletops (subcomponent) and table legs (subcomponent) and assembling them.
BOMs can also be made entirely of the same item in multiples - e.g. I sell a 10 pack of batteries (end product) by packaging ten individual batteries (subcomponent) together. In either case, these will be imported to Tradebox like any other standard products in your list.
If you hold stock of your end products (e.g. I always keep some 10's of batteries packaged up ahead of time) you'd use the Stock Transfer function in Sage to 'build' the end product; this adjusts out the subcomponents and adjusts in the end product. Stock transfer isn't tied to a specific sale, it's purely about adjusting inventory. This is the only way of using BOMs in standalone Sage 50 so it's what you'll have done if you were using Sage with BOMs prior to using Tradebox.
However many of our users don't hold stock of their end products and physically 'build' or 'bundle' them once an order is placed. To reflect this, make sure you've ticked the option Process BOM Transfers, which is held within each sales channel in the Sage 50 tab > Postings tab. Tradebox will record a sale against the end product record while automatically processing the stock transfer, so the adjustment effectively goes against the subcomponent.
If you're using Tradebox to upload product quantities back to the marketplace, it can also upload the 'potential' quantity available for each end product based on the free stock levels of the subcomponents (tick For Sage BOM use Qty. to Make Up in the sales channel Details tab).
Regardless of how you're using BOMs, the product mapping should be straightforward; each online SKU is mapped to a Sage end product that reflects it, and mapped without a multiplier. The adjustment out per quantity of subcomponents required is performed in Sage when Tradebox posts the order.