It’s the first day of a new month, and that can only mean one thing for my e-mail: more .pdf attachments than usual in my outgoing messages, in the form of invoices for one freelance client or another.

Instructing these companies to pay me for work done over the previous month should be easy after 11-plus years of not having a real job, but there’s still some struggle attached to this chore during and after the invoicing process.

The easiest part of it involves longer-running clients, where I just need to open the invoice document from the previous month, change the invoice number and the date, update the work done and the sum due, and attach the new file to an email.

But with less-frequent clients, I need to remember if there’s some wonkiness with a P.O. number or payment instructions that I may or may not have remembered to save in a previous version of the invoice file.

Others require their own format, usually a Google document or form or an Excel spreadsheet. Not knowing what kind of file a company will want me to produce before it will send me money is one of the things that’s kept me from following advice to use a professional accounting app like QuickBooks… another thing being my own apathy.

This routine can get more complicated if I’m away from home, since all of these invoice templates live on my Mac and since my Windows laptop doesn’t have a PDF-editing app equivalent to Apple’s Preview (sorry, Drawboard PDF). But keeping these financial documents in one folder on one computer allows for a simple accounting system: Right before I e-mail an invoice, I save it to an “Invoices – owed” folder, and once it gets paid I move it to an “Invoices – paid” folder.

It’s not the most sophisticated system, but it still seems to work after 11 years and change. At least when I remember to prepare and send the invoice in the first place. Which reminds me that I still have one invoice to finish for one client and a second to create for another, and of course they’re not in the same format.