For all my brothers and sisters living and working in the UK
www.gov.uk/marriage-allowance/how-it-works
This inshaAllah can benefit many, especially for families where the bread winner is the spouse with an income of less than £43K
Doesn't take long to sign up to it and you might as well do it as its just our earnings coming back to us, similar to child benefit money or Tax refund.
You will need yours and your partners NI number, Partners Passport details and DOB.
Obviously the one who earns the least amount or the one who doesn't earn a salary must apply. Either one of you can fillout the application as long as you have permission from your partner :) and all the details.