The use of special characters in the address fields of a customer results in the following traceback:

"avalara_salestax/sale_order.py", line 42, in onchange_partner_id
    res['value']['tax_address'] = str(unicodedata.normalize('NFKD', partner_name).encode('ascii','ignore') + '\n'+(addr.street or '')+ '\n'+(addr.city and addr.city+', ' or ' ')+(addr.state_id and addr.state_id.name or '')+ ' '+(addr.zip or '')+'\n'+(addr.country_id and addr.country_id.name or ''))
UnicodeEncodeError: 'ascii' codec can't encode character u'\xa5' in position 36: ordinal not in range(128)

This can be resolved by applying the same method used to handle the partner_name.