allow me to ramble & babble
Irrigation installations - get their own folder with address only on the tab. Names change over the years, addresses don't. Filed in alphabetical order by street address (name) in a filing cabinet.
Landscape installs - same as irrigation
Fert contracts - filed in alphabetical order by customer name by year. Stored in one big folder for each year.
Mow/Maintenance contracts - same as fert contracts
Irrigation work orders (not invoices)- one per customer per visit. Filed alphabetically by customer name in tab divided box. New box each year. Keep for several years in case someone says "you just" or "last year".
Computer generated customer invoices - in one binder by invoice number. New binder each year.
Vendor invoices - folder for each month. When we did landscape installs a copy of the vendor invoice went into the customer file so we new exactly what we bought and where for each job. For equipment parts or repairs a copy goes into a folder for the applicable piece of equipment.
Equipment - folder for each piece containing owner and parts manuals, parts purchases and service records. Manufacturer name followed by item model or name on tab. Filed by manufacturer name and file cabinet kept in the shop. Also keep vehicle titles and bill of sales in these. High value stuff like that is kept in the office filing cabinets. If you maintain equipment well and occasionally sell decent pieces of used equipment, folks are impressed when you pull out all the info to show them and it gets you premium dollar.