As has been mentioned in these articles before, one of the easiest ways to increase cash flow is to invoice more frequently. Who says that invoices can only be raised once a month or even once a week?
The larger the order, the more important it is to get the invoice out promptly.

Soft skills training for your accounts staff is vital. They should be checking in with your customers’ accounts departments as frequently as possible. In fact, it is a good idea to build friendly relationships with them so that you can ring them ahead of payments being due to check if payment is going to be made on time. If it is not, do not feel embarrassed about pinning them down to a date and holding them to it.

As well as ensuring there are no problems with external relationships that might impede cash flow, you also need to ensure that internal systems are everything they should be. For example, is everything banked on the day it is received? Is it possible to persuade clients to pay by bank transfer?

It is never too late to check the contracts you have with clients, or indeed, consider the standard contract terms you use.