We get asked this question at every single event we go to. And we have the exact same answer each time.
It is never too early to talk to an investor.
The days of a 30 page WORD document business plan with lots of embedded charts and images are long gone. All investors now prefer to engage with entrepreneurs informally, probably around a presentation to put some structure on the conversation. The presentation usually covers the basics of the team, the product / service, competitive differentiation, the economics (cost of customer acquisition, value or margin per customer, etc.) and a simple set of financials.
We love to meet entrepreneurs who are at the very early stages of putting their plans together. We might have some input or contacts that can help to move the business along. At minimum we can give our view on what it would take for us to invest in the business. We view these initial meetings as the start of a conversation.
Often, these very early conversations lead directly to a seed investment. Over the years we have invested with a number of founders who were still employed by other companies, often US multinationals, but were interested in putting together a start up. Our commitment of seed or venture capital provided the bridge to give them the confidence to leave their jobs and set up their new business. In over 90% of the investments that we make, the company is pre-revenue and often pre-product.