At present, Child Benefit is not means tested. From January, that's going to change. Where one partner or the other has income over £50,000, parents will gradually start to lose their entitlement, and one of them earns £60,000 it will be withdrawn entirely.
That sounds quite simple in principle but in practical terms it could be difficult. For a start, the higher earner may well not be receiving the child benefit to begin with, so one person could be receiving the benefit and another having to repay it (repayment will be via the higher earner's tax return, although you will be able to choose not to receive the payments to begin with if you know they'll just have to be repaid. And, in any case, it's not always the case that one partner knows how much the other earns - independent taxation is a fundamental part of the UK tax system. But apparently you'll be able to get just a "Yes" or "No" answer on that subject from HMRC (which to me is a massive invasion of privacy but there you go). Perhaps most absurdly, because self-employed tax bills are largely based on your accounting year, not necessarily the tax year, it's possible for someone to have a good year and consequently have to repay the child benefit of a partner they hadn't actually met until after that good year.
It remains to be seen how exactly things will work in practice but, in the meantime, just be aware of the effect it could have on your household budget. And if you don't have a household budget, consider drawing one up!
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