Up to £2 million people are entitled to a tax allowance they are not claiming.
We'll tell you more about this allowance which could be worth up to £900 to you...and counting.
The allowance in question is called the Marriage Allowance, and if you're eligible, you can easily claim to reduce any tax you or your spouse or civil partner pay.
And once you have signed up to apply for this, it will automatically be granted to you (or your partner) each year.
In very brief terms, one of you needs to be a basic rate tax payer, the other needs to be paying no tax because their earnings are not high enough to pay tax.
You can simply apply to HMRC to transfer £1,190 of the personal allowance (which dictates how much free pay each individual gets, ie their tax code) from the lower earning partner to the higher earning one.
The higher earning partner will then receive more tax free pay and pay less tax, making the tax paying partner £238 better off.
This allowance can be back dated for four years, meaning there is up to £900 to save here!
It only takes a few minutes to apply on the HMRC dedicated website. You will need both yours and your spouses NI number and a form of ID for you both, such as your passports.