Update regex for Swiss VAT numbers to match new format based on Swiss BID number

[danielterhorst]

Based on:

• https://www.ch.ch/en/value-added-tax-number-und-business-identification-number/
• https://en.wikipedia.org/wiki/VAT_identification_number

[ralphje]

I don't think the MWST/TVA/IVA is actually part of the CH VAT number. I believe it is actually part of the formatting of the number. We should remove that part in cleanup from the data, and format it accordingly for display. I think this is the best approach, as the choice for MWST, TVA or IVA actually seems te depend on the language context when it is displayed, not when it is entered.

See for instance the tables on http://www.bfs.admin.ch/bfs/portal/de/index/themen/00/05/blank/03/02.html (e.g. section Mehrwertsteuergruppe), the MWST-part is not shown in these tables. It would have it was actually part of the number itself.

On the other hand, I am still doubting whether the E-part of CHE should be part of the VAT number. It's there because Switzerland uses an alpha-3 code instead of an alpha-2.

[eriktelepovsky]

Hello. Please add "E" as a part of Swiss VAT number. Check this out: "CHE112355309"

https://vatapp.net/vat-number-check

[eriktelepovsky]

How to check Swiss VAT number?

Enter Swiss VAT number in the following format: CHE and number that can have 9 digits MWST/TVA/IVA. MWST/TVA/IVA part is optional. Swiss VAT number validation results are obtained in real time from UID register, The Swiss Federal Statistical Office (FSO) , Switzerland.

[ralphje]

I do agree that I was a bit too stringent five years ago. The intermediate solution would be to use the display class to fix this, though I agree it is probably best to store the E in the database at some point.

[eriktelepovsky]

Perfect :-) I am looking forward to accept pull request.

[eriktelepovsky]

Hello. Can you merge this PR, please?

[ralphje]

Not directly, I still do not agree that the TVA|MWST|IVA is part of the Swiss number. Furthermore, I do not think we should accept the E and keep it optional. It is either the E in there, or not. We should also adjust https://github.com/ralphje/django-internationalflavor/blob/master/internationalflavor/vat_number/validators.py#L22 to make sure that it inserts it when needed, so that this change is as transparent as possible.

Note that the display class already ensures that CHE gets printed for CH codes, so I'm not even sure that the issue is still actually there. It is just a matter of what to store in the database now.