From the Santander website:
What is a mortgage payment holiday?
If you’re adversely affected by coronavirus, the Government has confirmed that you may look to take a mortgage payment holiday on your residential or Buy to Let mortgage for up to three months to help your financial situation.
If you take a mortgage payment holiday, this means that you wouldn’t make mortgage payments for up to three months and we’ll add these payments onto your mortgage balance. As a result, your mortgage balance will increase and your monthly payment will be recalculated over your remaining mortgage term. Your monthly payment and the amount of interest you pay will increase for the remaining term of your mortgage. There is no fee for taking a mortgage payment holiday.
If your mortgage is not in arrears, the mortgage payment holiday will not impact your credit rating, and you will not go into arrears on your mortgage.
If your mortgage is already in arrears, please speak to us about the options available to you.
If you decide to take a mortgage payment holiday, you’ll receive a letter after each monthly payment is added to your mortgage balance confirming the exact amount of your new monthly payment.
Please be aware that if you pay by Direct Debit and your mortgage payment is due within the next 10 days, we will not be able to arrange the mortgage payment holiday for your next monthly payment. It will take effect from the following month.