Tax/admin tips for US-based consultant?

Best tool you can get initially is an accountant. :)

Seriously, not being a complete smart ass, just find a local accountant that can help you properly book your revenue and help you on taxes. It seriously doesn't cost much money and unless you are just doing tons of deals use either excel or something super simple like QuickBooks for your accounting. Quickbooks is nice because so many accountants are familiar with it and can set you up to where all they do is come in once a quarter and help you organize your taxes etc.

When you are starting off (wish I would've done this way back when) pay your estimated tax to a separate bank account every month, this will help make sure you don't get caught come tax time. Most likely what will happen is you will only pay a portion of what you saved for taxes since you'll have write offs etc that you can utilize.

So seriously the best tool I can recommend is an accountant to set you up and help you as you need it.

Outside of that: Quickbooks is a decent accounting package that will let you send invoices, book payments, services, and even can track time if you really need it to at some point. Many 8 figure businesses still run off quickbooks because it works for most common scenarios. I personally used an app (many exist) for tracking time because it was simple and would let me create jobs and track time against multiple clients which made invoice time easier. I even used it when I had consultants working for me to have them submit their time to me since the one I was using would send a CSV file of their time to job number and I could put those into an excel file and pivot out all the time to put together invoices easily.

I use Quickbooks self-employed: https://quickbooks.intuit.com/self-employed/ which imports from your bank account and exports to Turbotax (with free filing). It will remind you to pay quarterly taxes too.

If you use a separate business bank account (which you definitely should), it's very easy to set up rules to classify each transaction in their respective category for deductions so it's mostly set and forget. My only complaint is their invoice feature sucks so you still need to look for something else for that.

Turbotax should make this pretty run of the mill as long as you get all the proper forms from the people who paid you :)

The software will walk you through what boxes contain what values and then you type them in. Then maybe you can get some expense write offs too for home office, gas, computer etc if you saved the receipts.

Other than that be prepared to watch 30-50% or more of your income walk out the door depending on your state and level of income. That's why consulting is a hard gig that forces you to raise your rates!