Danish CVR

What it covers

Returns a valid Danish CVR (company identifier) with a correct mod-11 check digit. Use `format=vat` for the DK VAT number (`DK` + CVR). Set `invalid=true` for a CVR with a deliberately wrong check digit.

How it’s calculated

The Danish CVR company number's eighth digit is a weighted mod-11 check digit: the 11-complement of the weighted sum of the first seven digits, with the residue that would need a two-digit check treated as unissued.

Payload digits: 1,2,3,4,5,6,7 with weights 2,7,6,5,4,3,2.
Products: 1x2=2, 2x7=14, 3x6=18, 4x5=20, 5x4=20, 6x3=18, 7x2=14.
Weighted sum S = 2+14+18+20+20+18+14 = 106.
r = 106 mod 11 = 106 - 99 = 7.
raw = 11 - 7 = 4 (not 10 and not 11, so the check digit is raw).
Check digit = 4.
Cross-check via full-number rule with weights 2,7,6,5,4,3,2,1: 106 + 4x1 = 110, and 110 mod 11 = 0.

Edge cases

• A payload whose complement raw equals 10 (i.e. S mod 11 == 1) has no single-digit check and is never issued; the generator redraws such prefixes rather than emitting them.
• When the complement raw equals 11 (i.e. S mod 11 == 0), the check digit is 0 — a valid CVR ending in 0.
• Leading-zero CVRs are valid: the first payload digit can be 0, which the generator's edge mode deliberately exercises since a numeric parse would silently drop the CVR to seven digits.

Gotchas

• The generator passes weights for the seven payload digits only (2,7,6,5,4,3,2), not the full eight-digit weight vector 2,7,6,5,4,3,2,1; the trailing weight-1 term is the check digit itself and appears only in the equivalent full-number validation rule.
• The overflow rule is the primitive's default 'invalid': raw 10 -> undefined (unissued, redraw) and raw 11 -> 0. This is not a mod-10 fold, so no check digit is ever silently coerced.
• CVR numbers carry no sex, century, or category encoding — the seven leading digits are effectively opaque, so the only structural constraint on a value is this mod-11 check digit.