What documents should HOA boards review monthly?

At minimum: balance sheet, income vs. budget, aged delinquency report, open violations log, work order status, and bank reconciliations for every account.

Quarterly, add: reserve fund balance vs. plan, insurance coverage check, and an updated vendor list with current insurance certificates.

If your manager isn't producing these, ask. If they push back, that's a conversation to have sooner rather than later.