Where terms conflict
If you discover that your customer’s payment terms are different to your own, point this out and ask them to accept yours. Some terms may be negotiable, for example to increase or decrease, or change the dates of staged payments. Make sure whatever’s agreed is put in writing. If the customer won’t change their terms you have two choices: don’t accept the order / job, or do it on their terms. If it’s the latter, make sure you’re going in with your eyes wide open, and that you’ve assessed what impact it will have on your cash flow.