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What to include

To order a license: the codes and the edition (Full or Light), your Hardware ID, and the name and address for the invoice. The ordering steps are written out on the pricing page.
For a license problem — a key that stops working after an update, a move to a new computer, the two free additional licenses — the Hardware ID of the computer concerned and the release date shown in Help → About.
For a question about a calculation: the structure file (.mdl or .cha), the code and release, and what you expected to see.