Invoicing Software That Makes ACH Payments Easy for Clients?

I've reached one of those small business moments where getting a bigger client feels exciting right up until you realize your usual way of getting paid doesn't quite fit anymore.

Most of my invoices have been small enough that clients simply pay online using the payment options I already offer. Recently, though, I landed a much larger project, and the client asked whether they could pay the invoice by ACH instead.

It made me realize that as the size of my projects grows, I probably need an invoicing setup that grows with me too.

I'm not looking for a complicated accounting system just because one client asked for ACH. What I'd really like is something that makes bank payments easy for the customer, keeps the invoice and payment connected, and doesn't leave me manually checking my bank account wondering whether a random transfer belongs to invoice #47.

I'm completely open to moving away from my current invoicing platform if there's something that handles this more naturally.

For those who regularly accept larger invoice payments, what invoicing software do you use for ACH payments? How smooth is the experience for the client, and are there any fees, delays, or little frustrations you wish you'd known about before choosing your setup?

I'm less interested in a platform with a hundred impressive features and more interested in the one that quietly does its job when there's real money waiting to be paid.