@Bugsareinthebrook you’re right, it’s a bonkers system that people can deliberately work fewer hours, or keep themselves under employed, working in an easier (but lower paid) job than they are capable of. Tax credits were always a shit concept - it’s crazy that someone can choose to work less but end up with the same amount of money in their pocket as if they worked more. It would be far better to have a higher NMW so that the more you work, the more immediate financial gain you have. Plus of course, more affordable housing which would make life better for everyone.
But here’s the thing. Tax credits are no real alternative in the long run. They are, literally, just money in your pocket in the here and now. By deliberately remaining under employed, you aren’t making full pension contributions. You’re probably scuppering your chances of progression in the workplace. It’s taking the easy option in the short term but you’d probably regret it when the kids grow up, your tax credits dry up and you realise you’re stuffed in your older age.
I’ve seen people do what your BIL does... a friend of mine (capable woman, graduate, loads of experience in various jobs) dropped to 3 days a week, purely because she didn’t want to work full time. She was a single parent but to only one child, school age, so there were no child care issues, and in fact she had a great relationship with her ex and he had their child alternate weekends anyway so my friend had loads of time to herself. She was completely upfront that she was choosing this as an easy lifestyle choice because tax credits topped her up instead of working 5 days. I’m very fond of my friend but honestly, it was a disastrous decision. She’s now turning 50, her dc is mid- teens and my friend is realising that she has absolutely nothing behind her financially. She’s going to be getting poorer at a time when most of us want to be stepping back a bit and looking ahead to when we can draw our occupational pensions.
Tax credits have become a necessity for some people which is awful - wages should be enough to live on. For those like your BIL where they aren’t a necessity but a lifestyle choice, it’s a really daft route to take if you stop and think about it. It does nothing to secure yourself financially. Your BIL working part time and his wife not working at all... yes, tax credits will enable them to get by day to day, but that’s all. It’s not a sound financial foundation to build a family on.