This might sound obvious, but it's critical that you follow your Master Services Agreement, or MSA, to a T. You've possibly spent a great deal of time and money having your MSA hand-crafted and molded to your business. The Master Services Agreement spells out exactly how you expect business to be conducted. By having you and your customer sign the MSA, you both agree to all of the terms.
Since your Master Services Agreement is essentially the rulebook for your business relationship, what happens if one of you don't follow the rules?
Let's assume we have a customer that failed to pay on time. They're 37 days late and you're freaking out because they keep telling you they're going to pay "soon," but you haven't seen anything.
Your Master Services Agreement should clearly define when you invoice for managed services, how quickly payment needs to be processed, the types of payments you'll accept, and what happens when payments are late.
If your agreement states that invoices are created on the 20th, due on the 1st, and are late by the 10th, you need to also have "what next" defined. If a payment is late by the 10th, the 11th there should be a late charge applied to the invoice. There should also be something that states services may be suspended at a point; I recommend 30 days.
The important thing with suspending services is that you don't suspend their ability to access their files. The files belong to the customer, after all. If you're going to suspend Office 365 services you need to de-provision the license that you're (hopefully) getting from a CSP Distributor like PAX8, Synnex, or somewhere else. This gives the customer 30 days to either pay up and have a license issued back to their account, or get their own license.
It's important that you consistently follow the rules you've created with your MSA. Doing so will help customers understand you are a serious businessperson that has clearly defined processes and procedures.
There's a lot more to Master Services Agreements than how to get paid. If you want an Ohio Attorney Approved MSA just sign up for MSP Webinars. You'll get access to the MSA, a Statement of Work, documentation, vendor deals, and an entire community.