It's hard to avoid that some of the ONIX standard is based on retailer need -- which and that can be hard to know until you have a direct relationship with a number of them. Small publishers starting out don't have it easy. So for their benefit here are some general pointers in filling out your ONIX records:
Tax is easy: Ignore all tax related information slots in ONIX for North America American metadata (Europe is a whole different answer). Book tax in Canada and the US varies by province and state -- there's no unified way to express it that would apply to every jurisdiction. It is the retailer's problem to charge the correct tax based on where the sale is made using the province's or state's individual requirementlaws. A publisher really can't help them and in ONIX, if you have nothing to say, fill out nothing.
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(Proprietary codes in ONIX are codes that you choose to represent yourself. When you create one, make it a "code" and use it consistently: A "code" should be made of basic letters and numbers and ideally look like a code – a continuous string without spaces. Don't be witty – computer matching so does not care!. It should not look like a discount or any value that would be expected by the end users. For example, "40" may be your current discount but using 40 as a discount code will lead to problems. Someday the discount will change and your new and different discount will still be represented by a code value of "40". And don't be witty when creating codes or use easy to misread values.)
Having created the code(s) you should be prepared to tell any trading partner – a retailer who's agreed to do business with you – what it means for them. The code should appear in association with with every Price (that the retailer would reference) and represents the discount paid by that retailer on that product.
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Take your most complex business partner – the one with the most variation discount variations that needs to be accommodated – and create a code list based on their needs. Then assess other accounts – are there accounts: Do you need to create any extra variations? Once you have know all the codes you possibly variations that need applied to all the prices (remember that prices can be set for consumer sales and a number of institutions like libraries) you apply your code list. Each trading partner gets a defining table.be accommodated you can create the codes you need maintain accurate discounts. Then any retailer or other type of trading partner can get a defining table based on their discounts . Again for most small publishers there is one code and one discount for all products