My wife is an accountant, and here's a protip on how to make sure that a client never "overlooks" a payment: put a penalty clause in your contract that says the client is to pay 1.5% of the balance every month after the payment is due, and the client is responsible for any recovery fees. Your invoice will always be paid on time. If the client does not agree to this, walk away. It's a laughable amount of money, but their accounting department will front-load any "penalty" contracts nevertheless.

All this "overlooking" is bullshit anyway. Nobody would "overlook" you not doing any work for a couple of weeks. So why should it be any different when it comes to payment?

It's a great advice. If my job,as a consultant,is to consult them,their job is to make sure payments do happen and they happen on time. In my current job, I do have a decent visibility on when,who and why gets paid. And guess who gets paid first? A massive tech company, that threatens to suspend our system if we don't pay,which would mean the company going into ground.