Only discounts are allowed for the price, hence the only valid value is false (meaning an allowance)

Namespace
cbc urn:oasis:names:specification:ubl:schema:xsd:CommonBasicComponents-2
Data type
Boolean
udt:IndicatorType
Fixed value
false
Business terms
tir01-p004
Rules
Identifier/Error message Flag
PEPPOL-T01-B26301
Element 'cbc:ChargeIndicator' MUST contain value 'false'.
fatal