Many people assume everything they own will automatically go to their loved ones, but this isn't necessarily the case.
Without an up-to-date expression of their wishes, some or all of their property, possessions and cash may end up with people they didn't want to benefit.
And lack of planning could mean the heirs of those with larger estates have to share their inheritance with the taxman.
Many Scottish solicitors participate in this month's Will Aid, where law firms UK-wide waive their usual fee in exchange for a charity donation.
Karen Barrett – chief executive of independent financial advice website Unbiased.co.uk – says: "Too many people are unaware of the control that having a will gives you and its importance in ensuring your loved ones receive what you intended them to."
Across the UK as a whole, a third of over-55s and two-thirds of those aged 35 to 54 do not have a will.
Unbiased.co.uk says the most common reason is procrastination, with nearly one-third claiming they will act when they "get older", while more than one-fifth believe – often mistakenly – they have nothing of value to leave.
Others assume everything will automatically be distributed as they would have wanted, and a sizeable proportion of the remainder admit it has never occurred to them to write down their wishes.
If the worst happens, dying intestate – without a will – could add to the distress and financial suffering of those you are close to, particularly if they include a common law spouse or step-children.
If you weren't married or in a civil partnership, your partner has no right to your money or other possessions, and if you shared a home that was in your name only, they will face a legal battle to keep it.
No matter how close you are to any step-children, they will not inherit a thing without clear written instructions.
Meanwhile, if you were still married or in a civil partnership with someone else, even if you split up years ago, they could claim the bulk of your assets including your house.
You might want to leave property, cash or possessions to friends or to charities, but without a will, everything will be divided according to the law.
Under Scots law, if you leave no will, "prior rights" dictate that once your debts have been paid, your spouse or civil partner inherits any home you owned up to a value of £473,000, plus contents worth up to £29,000.
If you had no children, your spouse or partner gets other assets worth up to £89,000. If you had children, your spouse or partner gets the first £50,000 worth.
If you leave a valid will, prior rights do not apply, but you cannot completely exclude your close family.
If you had a spouse or civil partner and children, the former can claim a third of your moveable estate – everything apart from land and buildings – while the latter share another third. If you were childless, your partner has a right to half, and if you had no partner, the children take half.
Die intestate and once prior and legal rights have been satisfied, your children get everything that is left. If you were childless, your parents inherit. If they are dead, your siblings or – if you didn't have any – your spouse get the rest.
Without a spouse, more distant relations inherit, and if there are none, everything goes to the Crown.
Drawing up a will need not be expensive – a straightforward one prepared by a solicitor is likely to cost £150.
It is possible to get a kit on the internet for less, but Andrew Ogilvie, of Edinburgh law firm Connell and Connell, counsels against this. He warned: "We often have to go to court to rectify DIY wills."
Leaving a will that is out-of-date can be as devastating as not having one.
Mr Ogilvie says: "If you marry, have children, divorce, purchase a property or your other assets change, you really need to review your will."
It is particularly important to make a new one if you split up with a partner, as under Scots law, divorce and remarriage don't invalidate an existing will.
If your estate is likely to exceed £325,000, the threshold at which 40% inheritance tax becomes payable, you should consider ways to save this cash, such as gifting assets before you die or putting them in trust.
When Alexia Cordiner became a mother she decided it was time to face up to her mortality and write a will.
The Edinburgh 37-year-old, who is now a full-time parent to daughters aged five and three, explained: "If you don't have a will, it gives your family an extra headache when it's difficult enough that you've gone.
"I wrote the first one when my oldest girl was born and later updated it. When my partner and I got married last year, I updated it again and persuaded him to do one too."
Ms Cordiner was relieved to have her wishes down on paper. She said: "I felt a responsibility to my children to do it. It's almost like taking out car or house insurance."