I use credit cards or debit cards, and keep close track. I still have a
few net 30 accounts from when I was a contractor, but I do not tend to
use them.

Twice now I've had something odd happen with MSC. About a year ago
within minutes of using a debit card with them I got string of charges
or attempted charges that showed up as Inmate Solutions. I get instant
email (within a few minutes) notifications of all charges on that card.
I immediately canceled the card and reversed all charges, then mailed
MSC a check to cover their purchases. No big deal I guess, except I had
used several other cards and accounts on my computer that day and none
of them were compromised.

Yesterday I received an invoice in the mail from MSC. Now, I don't use
a net 30 account with them so it seemed suspicious to me. I looked
on-line at my account and no invoices matched the amount. Odd. So I
looked at invoices close to the claimed date, and found a payment from
one of my debit cards to MSC on the correct date. It too didn't match
any of the invoices. Now over a month later they sent me an invoice for
the difference. No calls. No emails. They just charged the wrong
amount and then sent me a past due notice 40 days later. Weird.

Just as I was starting to do more business with them again something
weird happens. As a one man shop I don't have the time to deal with
this sort of thing. I think they get moved back down my list of vendors
again.