If you are "cash basis," you would not pick up payment until 2013. However, if you bookkeeping is "accrual basis" then you would declare income from the date it was earned.
The following is from IRS Pub. P334-see "Example." [
www.irs.gov]
Cash Method
Most individuals and many sole proprietors with no inventory use the cash method because they find it easier to keep cash method records. However, if an inventory is necessary to account for your income, you must generally use an accrual method of accounting for sales and purchases. For more information, see Inventories, later.
Income
Under the cash method, include in your gross income all items of income you actually or constructively receive during your tax year. If you receive property or services, you must include their fair market value in income.
Example.
On December 30, 2011, Mrs. Sycamore sent you a check for interior decorating services you provided to her. You received the check on January 2, 2012. You must include the amount of the check in income for 2012.
Constructive receipt. You have constructive receipt of income when an amount is credited to your account or made available to you without restriction. You do not need to have possession of it. If you authorize someone to be your agent and receive income for you, you are treated as having received it when your agent received it.
Not my circus - Not my monkeys @(*.*)@
~Polish Proverb~