You ask for feedback and don’t hear back from them for weeks. And then they reply with “oh I thought I told you it was approved”.

Even worse, they leave invoices to go unpaid.

Work is slow and they (eventually) pay well but how do you deal with this?

First - I would make sure your contract details how you communicate and how you get paid. If you don’t have a contract get one, NOW!

Second - I would explain that all communications have to go through a project management system; something like Basecamp or Asana. That way, when you need something from them, like an approval, you can set them a reminder and it will ping them until they respond. And most systems keep an audit trail so you can see (and prove if necessary) that they didn’t reply or react to your questions.

Put these in place, give them a fixed time period (say 4 weeks) to improve how they respond and if they don’t then call it a day.

That’s how I would deal with it. What about you?