Martin Lewis has issued what he calls an 'urgent' warning to everyone who is married or in a civil partnership, asking all his followers on social media to 'please share' and get the message out there.
The Money Saving Expert founder is known throughout the UK for his savvy tips on keeping cash in our back pockets or bank accounts.
This ranges from how putting £1 in a bank account can give you a free grand every year to making sure we're not overpaying on our phone contracts.
He's also spoken candidly this week on how it feels to be the 'Money Saving Expert' when he himself is worth more than £120 million.
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In his latest advice, Lewis took to X (formerly Twitter), with his 'please share' warning when it comes to those who have tied the knot.
In a post, Lewis wrote: "Please share. URGENT!
"2.1 million couples eligible for marriage tax allowance are missing out, many are due £1,250 if you do it by 5 April."
What is the marriage tax allowance?
It's a way of upping your household income if you're shacked up.
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This only applies to you if you are married or in a civil partnership.
One has to be a non-income-taxpayer - earning less than £12,570 a year - while the other has to paying the basic 20 percent rate - which is up to £50,270.
You also have to have been born on or after 6 April, 1935 (if you're under 88, which most of us are, you're fine).
Lewis explains: "The non-taxpayer can apply to shift 10% of their £12,570 tax-free allowance to their spouse, so they can now earn £1,260 more (it's rounded up) without paying 20% tax on it.
"That's a gain of £252 per tax year."
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How do I claim the marriage tax allowance?
The beauty about the marriage tax allowance is that it can be backdated for five years.
"If you've been eligible since 2019/20 you can backdate it for a gain of £1,260, but go quick, or you'll lose the earliest year," Lewis says.
Going forward you also don't need to reapply, meaning it'll just keep landing in your bank account if you are still eligible.
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To get the full whack for the last five years, you need to do it by 5 April as Lewis advises as that is when the tax year ends and a new one begins. You'll lose one of the five years of money if you do it after then.
The non-taxpayer needs to apply for marriage tax allowance, and you can do so on the HMRC website here.
Topics: Martin Lewis, Money, Sex and Relationships, UK News
Tom Earnshaw