We are a VAT registered limited company and I do all the book keeping on a daily basis. Anything other that it would become unmanageable as we generate a lot of small to medium value invoices rather than a single one at the end of each week.
I wrote a simple excel spreadsheet in which we enter all our invoices each day.
On a separate page we enter all our expenses each day.
A third page tracks income and expenses and generates the quarterly vat return automatically.
Other pages we use to track directors loans and directors dividends.
It really is very simple and you're welcome to a copy of it if you wish, I could just email it over (email me if you'd like a copy).
Day to day we track money using an old copy of Microsoft Money which is effectively a bank statement generated daily by us as each transaction occurs - we reconcile this with our bank account on line daily.
On a separate spreadsheet I keep a track of stock, we stock check twice a year.
All this means when we come to submit our annual figures all we need to do is a final stock take on the last day of the year and submit all our figures to out accountant. For a few hundred pounds a year all our figures are done.
This may all sound like a faff, but it means any hour of any day we know exactly what our sales are and the financial position of the business. It also removes the once a year horror of wading through paperwork and trying to find fuel receipts from 10 months previously.
It should be easy for you guys, you certainly don't need to invest in things like Sage or Quicken - they are over complicated for you requirements.