Any valuation will be based on the expected sustainable level of future profits. Historic profits may well need to be revised if the level of remuneration for directors is different from what would be paid to competent but unconnected managers. In the past owner-directors typically paid themselves more than the market rate, but in recent years they have typically paid themselves less.
Eg a company turns in a profit of £100,000. However, the director's salary is only £6,000 and a manager would have to be paid £40,000 to do the same work. The "real" profit is only about £62,000, allowing for employer NIC. It's normal to look at three years trading with some kind of weighting to later years. Future profits will depend on how much the business depends on the current directors: if it won't work without them, then it's not worth much. Current market conditions can also adversely affect a valuation.
Assets may be a consideration for controlling or other substantial shareholdings, but not so relevant for small holdings.
Small shareholdings may be valued on a yield basis, and again if there has been a policy of excess dividends in past years that would need to be taken into consideration. It's normal to apply a discount, sometimes considerable, to small shareholdings. At the end of the day a 5% shareholding in a private company doesn't have any influence and may even be impossible to sell.
As I've said, the valuations for different taxes will be different. For example, if a 55% shareholder gifts 10%,for Capital Gains Tax you might value a 10% holding. For Inheritance Tax you value the existing controlling 55% holding
and the residual 45%, and the value of the gift is the difference between the two - that will usually be much more than the 10% on its own.
Ultimately there is only one real measure of value - the price that a willing buyer will pay a willing seller. Without that it becomes a theoretical and highly subjective exercise. Ten different valuers might give you 20 different values!
You also need to consider whether the company qualifies as a trading company. Even if it does trade, that's not automatic if it holds excessive cash reserves or investment properties. I have a client with a net asset value (before property revaluation) of £400k and with cash in bank of £512k. I think that there is a real danger of them not being treated as a trading company, which could be very, very expensive in terms of lost reliefs for IHT in particular, and have been nagging them to do something about it. However, they quite like their £500k bank balance (who wouldn't!) and are reluctant to pay the personal taxes to remove it.
And that's a brief summary of what's involved.
Did you start off by saying it was simple?