Primary does not mean automatically complete or unbiased. A provider's terms can establish its published wording, while a timestamped receipt can establish a different fact about an observed transaction.
Primary for which question?
A source is primary when it is an original record directly relevant to the question. Official bonus terms are primary for the promotion's published conditions. A bank receipt is primary for a payment event. A regulator's register is primary for its listed licensing status. None automatically answers every other question about the service.
An operator's statement that withdrawals take an hour is primary evidence of its advertised claim. A timed withdrawal record is different evidence about an observed event. Citing the first as proof that the second happened confuses what the source can establish. A secondary article may help locate either record but is not the original event itself.
Authority, scope and freshness
Inspect the legal entity, domain, date, market and relevant product. An old page can accurately describe a past offer while being unsuitable for current availability. A primary source can also contain errors or omissions, so the label does not eliminate the need for comparison and careful interpretation.
Building a useful citation
Link to the specific page or record where possible, identify the claim it supports and preserve the checked date. Avoid sending readers to a general homepage when the condition exists in a separate document. If sources conflict, record the differing wording and dates. Originality of the record and reliability of the conclusion are related but distinct questions.
In practice
An official promotion page is a primary source for its stated offer. A commentary article quoting that page is a secondary account and may omit conditions or use an older version.
What to check
Record the source identity, date, relevant passage and scope. Match the kind of evidence to the kind of claim rather than using one URL for everything.