The impact of cashing out a long service payment when I left my old job had a significant impact on my net worth (about 11% on my balance sheet and about 7% on the combined balance sheet) for the simple reason that no provision had been made in the balance sheet for this benefit. This was deliberate - it was difficult to value and in certain circumstances it might have amounted to a lot less than it did. The purpose of running a balance sheet is to help with my financial planning. Including assets which are of uncertain value and have the potential not to eventuate at all is more likely to harm than help my financial management.
However, receiving the payment did lead me to think about any other assets and liabilities which are not on the balance sheet. I came up with the following items:
1. a whole of life insurance policy taken out when I was at university. It matures when I am 50 and the amount involved would pay for a modest car or an extensive bout of travelling for us after I retire. The justification for not including this is the intention to spend it (unless I need it at the time);
2. a modest collection of claret in bond with UK wine merchants. While the wine could be sold, the amount is not large and it is likely that at least some of it is an investment in future drinking rather than financial well being;
3. paintings and carpets. The resale value of these is uncertain (but certainly small) ;
4. mrs traineeinvestor's jewelry. I strongly suspect that if I suggested selling my wife's engagement ring, she would list some of my surplus body parts on e-bay;
5. depreciating items such as furniture (or a car if we had one) would not qualify as investments and would never be included as assets in a balance sheet.
Even if the guesstimated value of items 1-4 above were added to the balance sheet, the effect would be minimal (about 1%).
I couldn't think of any liabilities which are not included in the balance sheet.