Invoicing setup is one page holding the four things that decide how quickly you get paid.
Payment processor
Connecting card payments lets a customer pay from the invoice rather than having to arrange a transfer or post a cheque.
This is the single largest lever on payment speed available to most small businesses, and it is usually underrated because the processing fee is visible and the delay it removes is not. An invoice paid in three days at a small percentage cost beats one paid in forty at no cost, every time — see days to get paid.
See Stripe.
Email domain
Invoices and reminders can be sent from your own domain rather than a generic address, once the domain is verified.
Worth doing before the first reminder goes out. An email from your business lands in an inbox; an email from an unfamiliar sender lands in spam, and a reminder nobody sees is indistinguishable from one never sent.
Verification is a change on your domain's settings, so it usually takes whoever manages your website a few minutes.
Email templates
The wording of what goes out. Four stages, escalating:
Friendly reminder — assumes it was an oversight, because it usually was.
Follow-up notice — firmer, still assuming good faith.
Urgent notice — names the consequence.
Final notice — the last message before this becomes a different kind of conversation.
Edit them once, in your own voice. The defaults are professional and impersonal, which is safe and slightly less effective than sounding like the person the customer actually dealt with.
Reminder schedule
How many days past due each stage fires.
Set them and leave them alone. The reason automated reminders work is not that the wording is clever — it is that they go out on time, every time, without anybody having to decide to have an awkward conversation. That hesitation is what turns a seven-day problem into a ninety-day one, and it is the thing being automated away.
A short message at around a week past due recovers most of what would otherwise age badly. See overdue invoices.
What it will not do
It will not decide who to stop working for. Chasing is automatic; the judgement about a customer who consistently pays at ninety days is yours.