I've been using Capsule CRM for a few months now, and I love it.
I've set up recurring "tracks," which are linear task lists for recurring things, such as "sole trader accounts and tax return." This in turn populates your to do list.
What I plan to do come April 6th, is to sort all my clients by March YE (a label I can attach to a client) then email them all requesting books in. I tick the "requested books in" task, then it reminds me in 14 days to ask again if I've not already had the books in.
This is how I plan to keep on top of getting info earlier this year...