upfront billing of professional services (“consulting”) is worse for a few reasons, (1) requires the customer to trust you more (they cannot withhold payment if you screw them or violate the contract) but generally the service provider is the riskier party (2) it causes service gaps (lost billable days) when the customer is late which is almost every month, (3) it requires you to define in advance exactly how many units will be billed and causes a service gap when you hit the retainer limit, (4) it gives the customer a natural ability to throttle billable hours which leads to unpredictable revenue. This all leads to higher bill rates, which is less palatable than a commitment to full time services contract. everyone involved wants predictable spend.

if this is an annual renewal payment for a saas, you need a process to follow which must include 60 and 30 day notices before the invoice, the rest varies greatly based on size - is this $1200/yr (credit card auto charge) or $120k (high touch sales rep)

It surely depends on what the OP is providing. If I was a consultant and the company stopped paying, I would obviously stop working for them on the next day. Otherwise, you could start charging weekly or daily instead of monthly. But then again, if they're not paying...

If I was providing a software or utility, the second you stop paying you are out. This actually happened to me in Japan because my mobile provider stopped sending paper invoices so I forgot to pay. I got cut off without any warning and as soon as I paid I got my access back.