The allowance or charge indicator is neither “true” nor “false”
`ChargeIndicator` must be exactly `true` or `false`. This code is returned on UBL documents; in CII the same checks carry the codes `PEPPOL-EN16931-R043-1` and `PEPPOL-EN16931-R043-2`.
Only the issuer holds this value: Factlint reports it and never fabricates it. Test your invoice to find out whether it is affected.
Why this error happens
XML accepts `1` and `0` as booleans; the rule does not. The indicator decides whether the amount is added to or subtracted from the total: its value carries a sign, and a spelling the recipient could read the wrong way is not tolerated.
How to fix it
Have your generator write `true` or `false`. Factlint does not normalise this value: it governs the direction of an amount, and an automatic correction that got it wrong would turn a discount into a surcharge.