Are out-of-network claims harder to get paid?

They can be, because plan rules may be narrower and reimbursement may work differently than for in-network care.

Should I pay an out-of-network bill right after a claim denial?

It is safer to review the denial reason and compare the insurer documents with the bill first, especially if the balance is large or confusing.

Out-of-Network Claim Denied? What to Check Before You Pay

If an out-of-network claim was denied, start by reading the denial reason and checking whether the claim was submitted correctly, whether the service had special authorization rules, and whether the provider bill matches the insurer documents. Out-of-network denials can involve both coverage questions and billing differences.