Contributions for Money Purchase and Profit Sharing plans come entirely from the employer, and must be made before the deadline.
In order for an employer to deduct contributions to a money purchase or profit sharing plan, the first thing that needs to happen is that the plan has to be set up by the last day of that year, which is generally December 31. SEP IRAs, which are different than money purchase or profit sharing plans, do not have to be set up until contributions are made, which can be up until the tax deadline (with extensions).
The deadline to make contributions to your money purchase or profit sharing plan is the same as the due date for Federal Income Taxes for your business, with extensions. An employer who filed a tax extension can make contributions to these plans up until the deadline for the extension.
How are My Retirement Benefits Computed?
How do I allocate my assets in retirement?