# stdnum.nl.btw

Btw-identificatienummer (Omzetbelastingnummer, the Dutch VAT number).

The btw-identificatienummer (previously the btw-nummer) is the Dutch number for identifying parties in a transaction for which VAT is due. The btw-nummer is used in communication with the tax agency while the btw-identificatienummer (EORI-nummer) can be used when dealing with other companies though they are used interchangeably.

The btw-nummer consists of a RSIN or BSN followed by the letter B and two digits that identify the number of the company created. The btw-identificatienummer has a similar format but different checksum and does not contain the BSN.

More information:

- https://en.wikipedia.org/wiki/VAT_identification_number

- https://nl.wikipedia.org/wiki/Btw-nummer_(Nederland)

    >>> validate('004495445B01')
    '004495445B01'
    >>> validate('NL4495445B01')
    '004495445B01'
    >>> validate('NL002455799B11')  # valid since 2020-01-01
    '002455799B11'
    >>> validate('123456789B90')
    Traceback (most recent call last):
        ...
    InvalidChecksum: ...

stdnum.nl.btw.compact(number: str) → str

  Convert the number to the minimal representation. This strips the number of any valid separators and removes surrounding whitespace.

stdnum.nl.btw.is_valid(number: str) → bool

  Check if the number is a valid btw number.

stdnum.nl.btw.validate(number: str) → str

  Check if the number is a valid btw number. This checks the length, formatting and check digit.