When you set up distribution sets you can indicate either accounts or distribution codes which the set will use.

Distribution codes specify the account and whether the detail will be a purchase, tax, if a tax – the tax rate etc.

The account and the distribution code are different things. Distribution sets can be simply accounts on which you will not see a tax rate or distribution codes (which for taxes will include the tax rate) or a combination of the two.

For more info please refer to you manual.

I hope this helps.