If you've taken advantage of your tax-free ISA allowance every year since the accounts were introduced in 1999, you should check how much you've saved as you may now have breached the UK's £85,000 safe savings limit.

ISAs, which come with the incentive of tax-free interest, were introduced by the Government in 1999 as a way to encourage people to save. They were rebranded NISAs earlier this month. (See our Top Cash NISAs guide for the best buys.)

Initially the maximum amount of money you could put away in one tax year was £3,000. This annual allowance has increased over the years, and now ISAs have become NISAs, you can save up to £15,000 tax-free each year (see the ISAs become bigger tax-free NISAs MSE News story).

If you put the maximum amount of cash into one of the top paying easy-access accounts at the start of every tax year (and topped up your account when this year's allowance increased on 1 July), and transferred previous tax years' ISAs into it, you could now be sitting on a balance of about £91,300, including interest.

But under the Government-backed Financial Services Compensation Scheme (FSCS), if your bank goes bust, only up to £85,000 is protected per person, per financial institution (see our Safe Savings guide for more info).

So if you've been saving in these tax-free accounts for years, check now how much you have stashed away.

Remember, a bank is not the same as an institution. Sister banks Halifax and Bank of Scotland's accounts are only covered up to £85,000 combined, but while RBS and NatWest are also sisters, their £85,000 limits are separate.

I've breached or am close to breaching the limit. What can I do?

If you've already breached the safe savings allowance, or you're close to doing so, transfer your old accounts, either in full or in part, to different institutions while leaving this year's £15,000 allowance in the same account.

If you're yet to open a NISA in this tax year, ensure you open one in a separate institution to your old accounts and don't transfer your old cash pot into it. As long as you spread your cash around so there's less than £85,000 with each institution, it's protected.

MoneySavingExpert.com's senior money writer, Helen Saxon, says: "If you've been a really savvy saver and now have more than the £85,000 savings limit, then for full protection, you'll need to transfer the extra to a different cash NISA.

"But beware – never just withdraw cash from one as it'll lose its tax-free status. Instead, ask the provider you're moving to to do the transfer for you."

See our Transfer Your Cash (N)ISAs guide for more on how to do this, as well as the best buys.

Will the safe savings limit rise?

The Financial Services Compensation Scheme's chief executive, Mark Neale, acknowledges that "the new £15,000 limit for NISAs does mean that those with some savings already, will reach the FSCS protection limit much faster than in the past".

But the FSCS says it has no intention of increasing the £85,000 protected savings limit.