Savers could be at risk of losing cash if they don't double check their bank has passed on the latest savings rate.
Saving rates have been rising after the Bank of England (BoE) hiked its base rate for the fifth time in a row to 1.25%.
When the base rate rises, lenders typically pass this on to customers by raising interest rates - although there is no guarantee they will.
Customers are now also being told to double check their bank is passing on any increases automatically, or whether they need to ask for it.
Has your bank asked you to call up to get the best savings rate? Let us know: mirror.money.saving@mirror.co.uk
The warning comes after This is Money was contacted by a Sainsbury’s Bank customer who says they were told to call up to apply the increase to his ISA.
The customer, known only as Craig, told the news site he had been stuck at 0.35% - despite the bank now offering 1.22% on its variable rate ISA on balances over £500.
He said: “I was surprised to be told that although Sainsbury's automatically decreases the rate on accounts if rates drop, I'm expected to contact it to ‘claim’ the new rate if its interest rates rise.”
In the terms and conditions for this type of account on the Sainsbury’s Bank website, it says: “We may offer different interest rates for new accounts.
“The interest rate on your account won’t automatically change to match the new rates.”
Sainsbury's Bank told The Mirror that it hasn't increased rates for existing customers, but reviews new rates “automatically” in line with the base rate.
We've contacted several other major banks to check their stance, with Santander also confirming that customers need to call up to ask for the higher rate.
It's worth double checking your rates to make sure any increase has been passed on.
HSBC, Lloyds Banking Group and Barclays said changes to savings rates would be applied automatically without a customer needing to ask.
Best savings rates right now
Saving rates are on the rise, so it's important to check you're getting the best value for money - and right now, easy-access accounts beat the top-paying ISAs.
The best-paying easy-access account is from Virgin Money, paying 1.56% - this is compared to the 1.4% from Cynergy Bank if you're looking for an ISA.
Personal Savings Allowance (PSA) rules introduced in 2016 mean most savers will be able to save a huge amount of money anyway without paying tax.
Basic 20% rate taxpayers can earn up to £1,000 interest a year from any and all savings without paying any tax on it. After that, their interest is taxed at 20%.
Higher 40% rate taxpayers can earn up to £500 a year, while top 45% taxpayers don't get a PSA.
So if you put your money away into an easy-access account paying 1.5%, you’d have to save nearly £70,000 to generate £1,000 interest.
Of course, you will get more interest on your money if you can afford to lock it away for a fixed amount of time.
The top-paying notice account is from Allica Bank, paying 2% and with a 95-day notice period to withdraw your cash.
For a one-year fixed saving, Cynergy Bank pays 2.72% right now, or 3.08% on a two-year fix - these are currently the best rates for both timeframes.
The best-paying five-year fix is from Monument Bank, which is offering 3.3%.
