It costs each household more than 200 every year, it raises more than beer and cider duty and it's rising faster than taxes on cigarettes - but half the population have never heard of Insurance Premium Tax.
Levied at 12 per cent on most general insurance premiums, IPT has doubled in the past three years - meaning policyholders are paying on average six per cent more for insurance than they did in 2015.
To put that into perspective, health insurance today costs on average117 more per year than it did three years ago, while comprehensive motor cover has risen by 25 and the cost to insure the family dog has gone up by 20.
When put together, the added costs to households represent a significant outlay- and experts worry the tax rate may rise again in this month's budget.
On top of this, think tank the Social Market Foundation - which crunched the figures on IPT - claims the tax disproportionately affects the poorest in society.
Its analysis of data from the Office for National Statistics has revealed that the poorest 10 per cent of society spend 3.1 per cent of their disposable income on insurance, excluding life insurance, which is exempt from IPT.
By comparison, the richest 10 per cent spend just 1.7 per cent of their disposable income on insurance.
To make matters worse if you live in an area with high poverty, costs like home and car insurance are more expensive - and as IPT is proportionate to the premium paid, this just adds to the pressures for people on low incomes.
It's not just households who have been feeling the pinch since the tax has doubled.
A study by Zurich Municipal found that a quarter of public services and charities have cut their level of insurance since 2015, when the tax was set at six per cent.
The survey found that nearly two in five public and third party organisations had to make tough decisions to cut budgets in their organisation and nearly one in 10 had to make job cuts in order to cover insurance costs.
One in five have comparably less cover in place as a result of the IPT rises, which leaves them exposed to higher expenses from claims.
Andrew Jepp, managing director at Zurich Municipal, said: 'Public sector organisations and charities are struggling to maintain the level of service and the required level of insurance protection as a result of repeated rises in IPT since 2015.
'The increasing costs from insurance taxation is forcing the public and voluntary sectors to make very tough decisions to reduce or cancel cover and increase excesses.
'This means they expose themselves to more risk which may leave them vulnerable to greater financial losses if the unfortunate happens.'
Experts are concerned that Chancellor Philip Hammond may decide to further hike IPT in this month's Budget on 29 October.
The fact that this will be the last pre-Brexit fiscal announcement coupled with pressure to keep the Prime Minister's promise to inject a further 20billion into the NHS by 2023 means tax hikes are expected.
There is usually a reluctance from policymakers to raise well-known and unpopular taxes such as VAT, income tax and fuel duty - making IPT a prime target.
Huw Evans, director general of the Association of British Insurers, said: 'The Chancellor should realise a raid on the responsible is the wrong way to balance the books.
'People buy insurance because it is a legal requirement or because they are wisely protecting their homes, businesses, families and health. Punishing these people with another tax rise would be inexcusable.
'Given the need to fund the NHS it would be particularly counter-productive to make health insurance even more expensive, forcing more people to rely on over-stretched NHS resources.'
IPT is a government-introduced tax on insurance policies, which was introduced in 1994.
It was introduced as it decided the insurance industry wasn't paying enough tax unlike other businesses, insurance isn't subject to VAT.
The amount of tax you pay on most types of insurance is now set at 12 per cent things like car, pet and home cover all fall under this bracket.
There's also a higher rate of tax, at 20 per cent, which covers things like travel insurance and certain specialist types of motor insurance, such as for vehicles designed for people with disabilities.
A small portion of the income raised is ring-fenced to pay for flood defences, but the majority goes straight into the Treasury's coffers.
And IPT is extremely lucrative for the Treasury it raises 4.8billion a year, which is more than beer and cider duties, betting and gambling duties, and air passenger duties.
Roughly half of this is paid for by consumers, the equivalent of 89 per household.The rest is paid for by businesses.
When the added costs to business are filtered down to customers, the Social Market Foundation estimates that IPT costs each household over 200 per year.
And according to OBR projections, IPT is set to raise more for the Government's coffers than inheritance tax will over the next three years.
Despite this, an Opinium survey found that half the population is unaware that IPT exists far more than any other tax.
Graeme Trudgill, of the British Insurance Brokers' Association, said:'We consider IPT to be an unfair tax that has the most negative effect on those who can least afford it and we continue to impress on Government the need to freeze this regressive tax.'