Ask HN: How do you handle clients who don’t pay on time?

I run a supply role at a company during the day and I’m building a B2B tool on the side. The problem I keep running into — both at work and in my family’s business — is that chasing overdue invoices is manual, awkward, and nobody has a good system for it.
Most small businesses I’ve talked to do one of three things: send the QB/Xero auto-reminder and hope for the best, send a WhatsApp message themselves when the reminder doesn’t work, or just let it slide because the relationship feels more important than the cash.
The second one is interesting to me. WhatsApp works — it gets read, it gets replies — but it’s completely manual and people do it inconsistently.
Curious what founders and operators here actually do. Are there tools that work? Have you found a workflow that doesn’t feel like you’re begging for your own money?