Young women, buy your car insurance before 21 December to save £250. Older men, save thousands by organising your annuity. And women of all ages – save as much as £2,000 by sorting out your life insurance cover.

An EU ruling will come into force on 21 December – dubbed "G-Day" – which will ban insurers from discriminating between men and women. It will have a dramatic impact on pricing across every aspect of the industry, but particularly on younger drivers and people about to retire.

Most insurers are refusing to reveal their rate changes until 21 December, but some have gone early.

Legal & General this week upped the average prices women pay for life insurance by 23%, but cut it for men by 3-4%. Endsleigh has equalised car insurance rates – with young male drivers saving hundreds of pounds, but at the cost of higher premiums for young women.

Prudential and Aegon have re-priced their annuities – and while men may be losing up to 6%, women gain as much as 11%.

Insurers fought a long battle against the rules, but were finally defeated by the European Court of Justice in March 2011 which gave them until 21 December to bring in unisex rates. Many insurers are planning to stay open until midnight on 20 December to accept applications.

Here we set out the impact of the changes – and what you can do ahead of the deadline.

Car insurance

Current situation Young males have always paid more than females. For an under 20-year-old, the difference could be £1,000 a year, reflecting higher accident rates and claims costs. But the differentials narrow once males reach their 30s and virtually disappear by the age of 40.

After equalisation Young males gain £500, young women lose £250. Big insurers, such as Direct Line and Aviva, still won't reveal their gender-neutral prices, citing commercial confidentiality. But Endsleigh, best-known as an insurer for students, has moved to equality already – and the changes are striking. GoCompare.com obtained quotes for an 18-year-old in Bristol driving a Ford Ka. The cheapest, Diamond, would charge £988 for a female but £1,871 for a male. Endsleigh offered £1,246, irrespective of sex. It was by far and away the cheapest deal for a male – an extraordinary £512 better than the next-best quote. But for women, it was £258 worse than Diamond.

What you can do A huge loophole in the rules mean that, so long as you conclude the contract before 21 December, you can start your policy after that date and not be affected by gender neutrality. So if you are a young female with a policy up for renewal in January, February or even March next year, you can find insurers who will quote now with the cheaper, non-equal price.

Direct Line will allow people to buy up to 20 December with a policy start date 90 days forward (ie 19 March). Aviva lets you buy 60 days forward. Adrian Flux, a specialist insurer, is writing to 350 female customers it thinks will benefit from buying before 21 December.

For young men, it's a very different story. If you have to renew before 21 December, try Endsleigh – it is coming in far cheaper than others. Other than that, you'll gain handsomely after 21 December. Remember to try the Guardian's compare-and buy service.

Annuities

Current situation Annuities are the jargon word for the income in retirement that pensioners receive from the pot of money they saved across their lifetime. Women have always received worse annuities than men because they live longer, and therefore the money they have saved has to be spread out over a longer period.

After equalisation Men lose 1-6%, women gain 6-11%. Women are the winners, with equality worth £4,000 or more in extra income from a £50,000 pension pot over 20 years – but at the cost of £700 or more to a man in the same position.

Prudential and Aegon have already begun pricing for gender equality, and Dean Mirfin at Key Retirement Solutions reckons that when the others reveal their figures, the hit on men could be even worse.

At Prudential, a man with £50,000 savings, retiring at age 65 and taking a "level annuity" (ie one that does not increase with inflation over time), will receive £2,506 a year now, but this falls to £2,467 following gender neutrality. A woman with the same pension pot will see her income rise from £2,277 to £2,467, a gain of 8.3%.

At Aegon the male sees his pension fall from £2,465 to £2,448 a year, but the female sees hers rise by 9.6% from £2,233 to £2,448. Men who wait until 75 to take their annuity receive an even worse deal.

What you can do Men, get your skates on and buy now, but women hold on for the better rates to come. Annuity transactions can take weeks to complete, so if men want to avail themselves of the better rates before 21 December, they should get a quote now. Shopping around is crucial. Rates vary markedly, and no one has to take the annuity offered through the pension provider they saved with. There are lots of brokers, such as Hargreaves Lansdown, Saga and Key Retirement Solutions.

Life insurance

Current situation Traditionally men have almost always paid more because, statistically, they don't live as long. According to Moneyfacts, a 35-year-old non-smoker would pay at least £6.23 a month for £100,000 of cover over 20 years while for women it is £5.49 a month.

After equalisation Women pay up to 23% more, men 3% less. The Treasury estimates life cover for women could go up by around 15%, while life insurance website Protected.co.uk puts the likely rise at 30%.

However, most insurers haven't yet declared their hands – and it is complicated by the fact that new tax rules for insurers, that will also push up prices, come in on 1 January.

One or two companies have switched to "gender-neutral" pricing early – notably Legal & General, which has upped the average prices women pay for life insurance by 23%. By contrast, for men it's typically around 3% less than a few days ago.

Prudential's "whole of life" cover went gender neutral earlier this month. On average, rates rose 17%, but this also reflects the tax changes, and some premiums fell, such as for some older men.

What you can do Women can still benefit from current prices, provided their policy begins prior to G-Day. However, if there are health issues that mean your application takes longer to process, this could delay things until after 21 December.

In short: act fast. Companies are offering different deals. For example, LV= guarantees that all applications received on or before 9 December will be processed on gender-specific rates. You can compare and buy life insurance deals here.

Income protection insurance/Critical illness cover

Current situation Income protection pays out a monthly sum if you can't work due to an illness or injury. Critical illness cover pays out a lump sum, for example to cover a mortgage, if you suffer a serious but non-fatal medical problem such as cancer, a heart attack or stroke. The latter is routinely bundled with a life policy. They can both be pricey, and watch out for exclusions. Income protection policies can be much more pricey for women at the moment – up to 70% more expensive than men's cover.

After equalisation Men will pay as much as 50% more. Again, most insurers haven't yet revealed their pricing. Experts predict income protection for men will rise by 20%-25%, while for females it will come down by around 28%, according to LV=. It reckons critical illness with life cover could rise by 6% for men and 16% for women.

However, as of this week, Legal & General says it will charge men an average of 49% more for income protection insurance, with women enjoying a 5% cut. For life insurance with critical illness cover included, L&G has hiked average premiums for women by 9% and cut them for men by 4%.

What you can do Now is the time to act before prices go up – and also in case of hold-ups which might delay things. Men looking for income protection cover should definitely get on with it, but women might want to wait.