Same concern. If GEO-IP location shows they are outside the country, and their home address is outside the country, want to give them the option of indicating that they are tax exempt.
This functionality is required in Canada and the EU.
Offer a second registration for the same event except this registration is specific to tax exempt attendees. As far as the U.S. is concerned, have a required field for their W-9 EIN and in custom email that goes out, you can ask them to email a copy including your registration confirmation number to match up to give the final approval of registration.
We ended up solving this by duplicating each event for every possibe tax rate that someone could be charged then developing a custom front end to DTRegister. When someone tries to sign up for an event, the custom front end asks all the required questions to determine the appropriate tax rate and also takes into account the Geo-IP location to prove (as required by Canadian and EU tax law the physical location of the client). It then transfers the client to the appropriate event with the correct tax rate.
We found a workaround for this in J1.5 2.7.18, by offering a VAT liability radio button. If Customers select Yes we add a field charge of 20%. If they select NO, they are asked to select a status, either: I am Outside EU (Registration can then continue) or I Have a valid EU VAT No.(Registration then offers a mandatory conditional field to collect the number).
Kudos to DTH for making a system flexible enough to offer a reasonable workaround. Small TSK for not building TAX checker plugin for online service and/or address lookup capability.
Having looked at the current setup built into DTRegister (J2.5 2.8.6a), they are nearly compliant. They just need to add an option to make a field conditional on one of the exempt codes you create in the backend. I guess a mix between option 1 and option 3 in the settings.
Unfortunately we have to keep using our version as it is fully compliant with the law rather than nearly compliant.
In addition the basket view isn't compliant either as it doesn't even include VAT per item or as a value on the total. We had to add that ourselves.