IsValidBankNumber ( banknummer )

Checks a Dutch banknumber for validity.

Average rating: 3.9 (35 votes) Log in to vote

Theo Ros - Show more from this author

Sample input:

IsValidBankNumber ( "123456789" )

Sample output:

false

Function definition: (Copy & paste into FileMaker's Edit Custom Function window)

/*-------------------------------------------------------
Function Name: IsValidBankNumber
Checks a Dutch banknumber for validity.
Syntax: IsValidBankNumber ( banknummer )
Returns "true" if banknummer passes the '11-proef', 
"false" if not or an empty string if banknummer is empty.
Author - Theo Ros
----------------------------------------------------------*/

If ( IsEmpty ( banknummer ) ; "" ;
  Let ( sNumber = Filter ( banknummer ; "0123456789" ) ;
    If ( sNumber = "123456789" or Length ( sNumber ) > 9 ; "false" ; 
      Let ( nNumber = Right( "000000000" & sNumber ; 9 ) ;
        If ( Mod( GetAsNumber ( Left ( nNumber ; 1 ) ) * 9 +
          GetAsNumber ( Middle ( nNumber ; 2 ; 1 ) ) * 8 + 
          GetAsNumber ( Middle ( nNumber ; 3 ; 1 ) ) * 7 + 
          GetAsNumber ( Middle ( nNumber ; 4 ; 1 ) ) * 6 +
          GetAsNumber ( Middle ( nNumber ; 5 ; 1 ) ) * 5 + 
          GetAsNumber ( Middle ( nNumber ; 6 ; 1 ) ) * 4 +
          GetAsNumber ( Middle ( nNumber ; 7 ; 1 ) ) * 3 + 
          GetAsNumber ( Middle ( nNumber ; 8 ; 1 ) ) * 2 +
          GetAsNumber ( Right ( nNumber ; 1 ) ) ; 11 ) = 0 ; "true" ; "false"
        )
      )
    ) 
  )
)

Returns "true" if banknummer passes the '11-proef',
"false" if not or an empty string if banknummer is empty.

Comments

		Thibaud, Amstelveen, NL Apr 15, 2012
Bank ING has a serie of bankaccounts that does not follow your algoritm. Those are the former 'Postbank' accounts. Is there a way to check those too?

		Theo Ros, Hilversum Apr 15, 2012
for Postbank numbers there is no validity check. The only thing you could do with those is that the numeric value must be less than 100.000.000 (100 million). Only ING (Postbank) can check if it is a valid, issued number..

Note: these functions are not guaranteed or supported by BrianDunning.com. Please contact the individual developer with any questions or problems.

IsValidBankNumber ( banknummer )

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