Why this number comes before any policy decision
Before you can work out how much cover you need, you need to know how long your household could manage without any income at all. That stretch of time, from the day you stop earning to the day money starts arriving again, is what everything else rests on.
It decides how long a deferred period you could survive without a policy paying anything. It also decides whether a given amount of cover would close the real gap or leave a shortfall underneath it. Working this out with your own figures is the sensible starting point, before you look at any policy at all.
What fills the gap, and for how long
Three things carry a household through the period before income resumes: savings that can be drawn on, any sick pay still arriving from an employer or the state, and any other income the household has, such as a partner's wage or rental income. Measured against what you spend each month, the number of weeks those three can cover is what tells you how exposed your household is.
Savings you could draw on
Not every saved pound is available. Money tied up in a pension, or set aside for a known future cost such as a tax bill, isn't there to cover lost income even though it sits in an account with your name on it. The figure to use is what you could draw on without creating a second problem.
Outgoings that keep running
A mortgage or rent, utility bills, loan repayments and insurance premiums don't pause because you've stopped earning. Groceries and discretionary spending might come down a little, but the committed part of your monthly spend is usually close to fixed. That fixed figure is what your savings have to outlast.
Sick pay and other income still arriving
Employed readers may have employer sick pay, statutory sick pay, or both, for a number of weeks before it stops. Self-employed readers generally have none of this, which is one reason the gap looks very different depending on how you work. A partner's income, if there is one, extends the runway and should be counted.
What statutory sick pay leaves you with
Statutory sick pay is the lower of the weekly rate and 80 per cent of your normal weekly earnings, for up to 28 weeks, under the Social Security Contributions and Benefits Act 1992 section 157 as amended from 6 April 2026, in England, Wales and Scotland. The 80 per cent part is easy to miss. Anyone earning above a certain level doesn't get the full flat rate, they get whichever figure is lower, and for many earners that isn't the flat rate at all.
Statutory sick pay also doesn't reach the self-employed. If you work for yourself, the weeks your household can run on are set entirely by savings and whatever other income you have, with no state sick pay underneath you. Statutory Sick Pay and What It Leaves sets out what the 28 weeks cover and what's left once they end.
How this number sets the deferred period you can afford
The deferred period is the gap between the day you stop work and the day a policy starts paying out, commonly four, eight, thirteen, twenty-six or fifty-two weeks. A longer deferred period generally brings the monthly premium down, but only helps you if your household can last that long without any policy paying out.
This is why the two numbers need working out together: the weeks your savings and sick pay can cover, and the deferred period a policy offers. Choosing a deferred period longer than your household could manage leaves a stretch with no income from any source at all. How Long Could You Go Without Income? works through this with your own savings, outgoings and sick pay entered directly, and shows which deferred periods you could carry.
Common mistakes people make when working this out
- Counting savings that aren't liquid. Pension pots and money earmarked for a tax bill aren't available to cover lost income without creating a second shortfall.
- Assuming outgoings will fall. Rent, mortgage payments and loan repayments carry on regardless of whether income does.
- Treating statutory sick pay as a flat amount. The 80 per cent of normal weekly earnings rule means higher earners often get less than the headline weekly rate.
- Using a single average month for self-employed earnings. A lean month or a lean year changes the figure an insurer would use to set the maximum you could claim. That's a separate question from how long your savings could cover you on their own, and Income Protection When Your Income Varies covers how insurers establish that figure.
Working it through with round numbers
Take a household with £2,000 of committed monthly outgoings and £6,000 in accessible savings, with no sick pay or other income arriving. On its own, that household could manage for twelve weeks before the money runs out. Add employer sick pay on top, for however many weeks it lasts, and the runway extends further before any gap opens up.
These figures are illustrations to show how the arithmetic works. Your own savings, outgoings, sick pay and other income decide your own number, and it's worth checking that figure before you compare deferred periods or cover amounts with an insurer or a regulated adviser.
Once you know your number
Knowing how many weeks you could manage tells you what deferred period is realistic. It doesn't yet tell you how much monthly cover you'd need once a policy starts paying, or whether that amount is one an insurer would sell you. How Much Cover, and for How Long? takes the outgoings figure from this exercise and checks it against the cap insurers commonly apply to pre-tax earnings.
It's also worth knowing, before any of this becomes more than a calculation, what a policy would actually count as being unable to work. What 'Unable to Work' Means in a Policy sets out the three tests a claim is judged against, and Making a Claim covers what happens from the day you stop working to the day a claim is assessed.