You may have been given an ISA as a gift, or got one out to try and make the most of your money, but some banks have been hacking away at the worth of your savings, making 171 cuts in 6 years.
Some people are getting screwed out of £178.50 a year!
According to Which?, some banks are considerably worse than others, as they crunched the numbers on 212 instant-access cash ISAs from 21 banks and building societies.
Their research looked at cuts for existing ISA customers, rather than those with bonus rates expiring and the like.
Which? said NatWest had the largest amount of cuts per account, with eight across two accounts over six years.
The bank's e-ISA used to earn savers 2%, but for those who haven't moved their money will now be getting a paltry 0.25%.
Which? also saw that Tesco Bank had made three rate cuts on one account, and at RBS, they'd made two cuts on one account, and Barclays made 13 cuts across seven accounts.
As for those treating customers a little better, the Principality Building Society came out on top, with only one cut across five ISAs, while the West Bromwich continue to pay existing customers a 1.25% to 1.55% rate they signed up to.
Harry Rose, Which? Money editor, says: "Many savers simply want a provider they can trust to keep their ISA rate competitive. Too many banks are paying truly woeful rates of interest or are scissor-happy when it comes to cutting rates often penalising their most loyal customers."
"Our research shows savers who don't want to have to keep moving their savings about should consider parking their cash with one of the more reliable building societies who have been better at not cutting their rates for existing savers."
So, shorthand - the worst banks for cutting ISA rates are, in order:
- Tesco Bank
- M&S Bank
A spokesman for the British Bankers' Association (BBA) said: "These have been frustrating years for savers. The Bank of England's base rate has remained at a record low for several years and whilst this has been good news for borrowers it has fostered a low interest rate environment which has not been easy for many savers to bear."
"During this period banks have made it easier for savers to find the right products for their needs. The electronic cash Isa transfer service has helped to significantly reduce switching times, interest rate disclosure on savings accounts has improved and a number of providers have streamlined their savings ranges to help customers to navigate the market."
"The introduction of the new personal savings allowance from this April means that most savers will no longer have to pay any tax on their cash savings. We always encourage customers to review their savings regularly and to shop around for the best deal for them."