You can invest up to £5,640 in a cash ISA this tax year, and the same amount in stocks and shares. While officially the tax year finishes on April 5, providers can choose when they want to stop accepting applications, so it pays to know the major providers’ deadlines so you don’t miss out on the deal you want.

Here, we look at some of the best cash ISA deals currently available, and when you need to apply by…

Top variable rate ISAs and deadlines

Some ISA providers require customers who want to take out their 2012/2013 ISA online or by telephone to act before the end of the March.

For example, anyone wanting to apply by telephone for either NatWest or Royal Bank of Scotland’s e-ISAs, both of which pay 2.25% tax-free on balances of £30,000 or more, must do so by March 28 at the latest, as from Good Friday on March 29, the banks will no longer accept phone applications for the 2012/2013 tax year.

New customers wanting to apply for either of these ISAs online must act even earlier, as any application made from March 26 will not be completed in time for 2012/2013 tax year. However, existing customers have longer. Once logged into online banking, they can open an ISA up to April 4, and then move funds the next working day.

However, if you want to apply for a NatWest or RBS ISA in branches, the deadline is April 5. A spokesman for RBS and NatWest said; “Telephone and online applications have earlier cut-offs due to paper applications needing to be sent and returned. With Easter week falling just before the end of the tax year, we cannot guarantee they will be open in time, so we're taking a cautious approach.”

Other providers, however, offer later deadlines. Barclays Bank Instant Cash ISA Issue 1, which pays 2.30% on a minimum investment of £30,000, can be opened online up until 11pm on April 5.

If you want to apply for the account in person at a branch, a spokesman for Barclays said that several will remain open later than usual on April 5, with some even open until midnight. However, the bank said it couldn’t yet confirm which branches would be open this late, although advised that it would be those in the most heavily populated areas.

The current market-leading variable rate cash ISA is Santander’s Direct ISA Saver (issue 1), which pays 2.50% (variable) for the first 12 months. Thereafter returns will drop to a variable rate, currently paying 0.50%. You’ll need a minimum £2,500 to open the account which accepts transfers in.

Cheshire Building Society's ISA Saver account, is also easy access and pays a lower annual interest rate of 2.30% tax-free, although you only need a £1,000 minimum deposit. The rate includes a 2.00% bonus payable until July 31, 2014 and, again, you can also transfer in money held in existing ISAs.

A spokesman for Cheshire said that no final deadlines have yet been set for 2012/13 ISA applications, but confirmed that a decision on this would be made at the end of March.

This account can be opened with a minimum investment of £1,000, and you can also transfer in money held in existing ISAs.

Other competitive deals include Tesco Bank’s Instant Access Cash ISA which pays 2.30% annual interest tax-free. This rate includes a 0.30% bonus for a year, and can be opened with a minimum investment of £1. You cannot make transfers into this account from previous years’ ISAs.

A spokesman for Tesco said: “The deadline for both online and telephone applications is April 5. However, we would encourage customers to complete their application as soon as possible to allow any additional documentation requests to be completed.”

GE Capital Direct’s GE Saver Cash ISA pays 2.25% tax-free on a minimum investment of £500, but again this account doesn’t accept transfers from existing ISAs.

GE Capital Direct said that it couldn’t currently give any information on ISA deadlines, but its website states that “to ensure availability apply now as our GE Saver Cash ISA can be withdrawn at any time,” so savers interested in this account should get their applications in as soon as possible. 

Nationwide Building Society’s Web ISA Issue 2 pays 2.25% on a minimum deposit of £10,000, but this rate includes a 1.75% bonus until the end of August next year, so savers will need to move their money once this disappears. New customers will need to open a card account with Nationwide before they can open this account. Nationwide said it couldn’t yet confirm the final deadline for 2012/13 applications, and said this would be decided at the end of the month (March).

Top fixed rate ISAs and their deadlines

If you are considering investing this year’s cash ISA allowance in a fixed rate ISA, you should again act sooner rather than later if you don’t want to risk missing out.

Santander's MAJOR ISA 2 Year Fixed Rate pays a tax-free fixed rate of 2.80% a year plus an additional 0.10 per cent bonus if Rory McIlroy wins an eligible golf ‘Major'. If you have a Santander 123 current account or 123 cashback credit card, you will benefits from an even higher rate on the Major ISA as the ‘123 Exclusive’ version of this account pays 3.00% tax-free fixed, plus an extra 0.10% if Rory wins a major.

For savers wanting instant access to their tax-free savings, Santander also offers a Direct ISA Saver account, which pays 2.50% annual interest tax free. You need a minimum investment of £2,500 to open the Direct ISA Saver account, and after 12 months the account reverts to an ISA Saver account, currently paying up to 2.00% tax-free with no bonus.

Santander said it will accept online and phone cash ISA applications until midnight on Thursday 4 April 2013. If you make your application in a branch, you have until April 5. A spokesman for Santander said; “ISA applications will be accepted by branch closing time on Friday 5 April, but customers should make an appointment first. Customers should check their local branch opening times in advance to avoid disappointment.” 

NatWest and Royal Bank of Scotland have also just launched new two-year fixed rate ISAs, paying 2.25% annual interest tax free on a minimum investment of £1,000. The deadlines to apply for these ISAs are the same if you are using your 2012/13 allowance are the same as those outlined for its e-ISAs.

Please note: Any rates or deals mentioned in this article were available at the time of writing. Click on a highlighted product and apply direct.