Ust ID Nr. (Umsatzsteur Identifikationnummer, the German VAT number).
The number is 10 digits long and uses the ISO 7064 Mod 11, 10 check digit algorithm.
>>> compact('DE 136,695 976')
'136695976'
>>> is_valid('DE136695976')
True
>>> is_valid('136695978')
False
Convert the number to the minimal representation. This strips the number of any valid separators and removes surrounding whitespace.
Checks to see if the number provided is a valid VAT number. This checks the length, formatting and check digit.