Thanks for getting in touch with us about this, @gacpool,
Allocating funds is an important part of your finances and books. With this, we always recommend consulting an accountant for proper accounting advice. If you don't have one, we can help find someone near you.
You can create journal entries to transfer funds from revenue to a liability account. See this:

Regardless, this step is something you have to confirm with a professional to ensure you're doing it right.
Another option to save funds is creating a holding account to where you can put the balance from revenues. You will then use this account to pay off the liability when the project is done.
To create a holding account:
- Go to the Gear icon and select Chart of Accounts.
- Click New.
- Choose Bank for the Account type. Under Detail Type, pick Cash on hand.
- Then name the account Holding Account.
- Once done, press Save and Close.

To move funds, you can use a journal entry debiting the holding account and crediting the revenue account. Then, when you pay for the liability, use a check. See this:

If you have additional questions about this, feel free to get back to me or mention my name. I'll be right here to help you anytime. Have a nice day!