Summary
Here are a few mistakes I've made in accounting:
Not photocopying checks / deposits before making the deposit
Later, when looking at the statement, I can remember that several items were included in the deposit, but I couldn't remember the break down. I don't have a photocopier at my new office yet, so I'm just writing down the checks on the deposit receipt the bank provides. [http://www.pbooks.org/blog/2009/03/deposited-check-images.html Bank of America now provides scanned images of checks through online banking]!
Counting income twice
This was a dumb mistake on my part. I would recognize the income when issuing an invoice, and then also count the deposit as revenue. In the first place, I matched the revenue to accounts receivable, and then debited accounts receivable when the payment was deposited.
Counting Loans as Income
Another big mistake!
Not doing my bookkeeping tasks regularly and frequently
Waiting to long to reconcile accounts can make it a bigger undertaking than it needs to be. My new strategy will be to reconcile accounts once per month.
Using Credit Cards
Credit card companies make it impossible to resist using them. For my business, it wasn't a good idea, but not for the reasons you might think. By using credit cards, I was able to leverage lower interest rates, rewards, and cash back - a boon to the bottom line. However, the problem with this is that it created a bookkeeping nightmare. There were tons of transactions all over the place. My accountant advised instead just to use my checkbook - it keeps everything in a single account and is much easier to maintain. Unfortunately, not all my vendors accept checks. Many only accept credit cards. My goal now is to only use one credit card.