Processing
Book-keeping as a job is processing a flow of data - recording the invoices, cash receipts, bills, and other transactions that arise. In a busy organisation this flow can be relentless and having a method to handle this flow makes the job far easier.
The simulations have organised the work for you, but in reality the book-keeper for a small business may well also be the person opening the post, or be handed a carrier bag of paper, or given access to a group of Dropbox files online - and have to make some sort of sense of it all. Non-book-keepers don't always help by including irrelevant data or assuming the book-keeper is psychic and all-knowing.
Here is a suggested approach, shown as a flow. Click each one for more.
The six steps shown here are not rules and every job will have its idiosyncrasies. You will need to develop your own way of getting the job done and adapt the systems accordingly.
Dealing with e-data
If the data is in electronic form, either on a local machine or on the web then it's easy for files and information to quickly become duplicated, confused and lost.
To avoid this, create a sense of flow by keeping unprocessed e-documents in a different place to processed ones, and make sure processed e-documents are archived effectively.
For smaller businesses, printing bills and receipts rather than relying on electronic archives is often more practical, but there are obvious advantages in relation to cost and storage space to keeping the data in an electronic form as long as the archives are stable and secure and regularly backed up. Marking-up e-documents can be fiddly and time consuming so keep it simple. Try to create separate files for each transaction. Use Acrobat Professional or something similar to make pdfs of web pages. Pdfs tend to make better e-documents than Excel or Word files.
Links to web pages generated when making online purchases are too transient to be suitable as evidence for transactions.