The VAT point date is declared twice
The value added tax point date (BT-7) and the code that designates it (BT-8) are mutually exclusive: the invoice carries one or the other, never both.
Only the issuer holds this value: Factlint reports it and never fabricates it. Test your invoice to find out whether it is affected.
The message your validator prints
Copied verbatim from the sealed artefact: this is the exact sentence the check prints when this rule fails.
[BR-CO-03]-Value added tax point date (BT-7) and Value added tax point date code (BT-8) are mutually exclusive.
Quoted from schematron-cen 1.3.16, licensed under EUPL-1.2.
Common searches around this code
These phrases mirror what an integrator searches for: code, syntax, rule, business field and correction.
Test your file with this error in mind
Upload the invoice involved: the report will say whether this code appears, where it appears in the document, and whether Factlint can only report it or also fix it.
To automate this check in an ERP flow, call the validation API and link every returned code to its public page.
Why this error happens
The two fields say the same thing in two ways — an explicit date, or a code pointing at the event that determines it (delivery, payment, issuing). A template that fills both goes unnoticed as long as the second stays empty by default, and trips the rule the day a setting switches it on.
How to fix it
Keep whichever of the two your tax regime makes correct and remove the other. The choice commits the date the tax becomes chargeable: it belongs to the issuer, not to the file.
XML correction example
<ram:TaxPointDate>…</ram:TaxPointDate> <ram:DueDateTypeCode>5</ram:DueDateTypeCode>
<ram:DueDateTypeCode>5</ram:DueDateTypeCode>