What's the adjective for substantiate? Here's the word you're looking for.
Included below are past participle and present participle forms for the
verbs substantialize and substantialise which may be used as adjectives within certain contexts.
“That is why the legislator requires that the requests for deletion be made in writing and be accompanied by substantiative documents so as to protect the citizen's right to vote.”
“But there's not enough time to make substantiative changes by next year's legislative session, he said.”
“I first read his poetry online, so I asked whether he thinks there is a substantiative difference between reading poetry online versus on the written page.”