How many top-level folders should a small business have?

Usually between five and eight. Fewer than that and folders become dumping grounds; many more and people can't remember where things go.

Should folders be organised by year or by customer?

Finance is usually easiest by year. Customer and supplier work is usually easiest by name.

How do I stop the structure getting messy again?

Agree a naming convention, empty the Unsorted folder regularly and consider a tool that files new documents automatically.

The best folder structure for a small business

A good small-business folder structure has a handful of top-level folders based on how the business works — typically Finance, Customers, Suppliers, People, Marketing and Policies — with the same subfolders repeated inside each and a clear naming convention. Keep it no more than three levels deep.

An example structure

Finance — by year, then Invoices, Receipts, Bank, Payroll
Customers — one folder per customer, then Quotes, Contracts, Correspondence
Suppliers — one folder per supplier
People — staff documents (restrict access)
Marketing — brand assets, images, campaigns
Policies & insurance
Unsorted — a temporary holding area

Rules that keep it working

Limit depth to three levels.
Name files with the date first (YYYY-MM-DD).
Never save to the desktop or Downloads as a final location.
Agree who can create new top-level folders.
Empty Unsorted weekly.

Moving an existing mess into the new structure

Create the new top-level folders first, then work through old folders one at a time. Move whole folders where you can, and leave anything uncertain in Unsorted rather than guessing.