The stake. Two registration numbers belong on a UAE tax invoice, and they come from two different records. Yours is a property of your company. Your customer's is a property of their contact. The pack prints both and prints nothing where nothing has been stored, which is the correct behaviour and also the reason a first print so often looks half-finished.

The mental model. No configuration is required to print — install the pack and the forms work. That is unusual enough to say plainly. Two things are still worth setting before anything goes to a customer, and the first is your own TRN, the Tax Registration Number that the Federal Tax Authority (FTA) — the federal body administering VAT and Corporate Tax in the UAE — issues to a registered business. The tax invoice prints it, and without it the field is simply blank.

Where to look. Set your own TRN under Settings → Companies, or on the UAE tax configuration — either location carries it. Set your customer's on their contact, in the Tax ID / VAT field. Both are ordinary records your team already maintains, and neither is a setting buried inside the print pack.

The worked example. Take an invoice you will meet again in the next two lessons: three lines to one UAE customer, AED 40,000 of standard-rated goods at 5%, AED 25,000 of zero-rated supplies and AED 10,000 of exempt supplies. Printed on the FTA Tax Invoice with both TRNs in place, the header carries your company name and your TRN, the customer block carries their name and their TRN, and the totals read AED 75,000 net, AED 2,000 of VAT and AED 77,000 due. Print the same invoice with the customer's Tax ID / VAT left empty and every one of those figures is identical — the arithmetic was never the problem. One field is blank, and it is the field that identifies who you invoiced.

The failure mode. The tax invoice shows no TRN. Set the company's TRN, and the customer's on their contact under Tax ID / VAT. There is no third place to look and nothing to switch on: a blank TRN on this form always means an empty TRN field on a record behind it. Fix the record, print again, and the field fills.

The idea to carry forward: the form is a window onto your data. Anything it prints blank is blank somewhere behind it.