Under current plans, employers are compensated for the costs of hiring someone new to replace a reservist going away on operations, or for overtime costs for other employees.
Hammond said a further cash bonus would give small businesses "more reasons to employ reservists".
Speaking to BBC Sunday Politics, he said the size of the cash incentives was still being decided but added: "By the time we publish the White Paper later in the spring, we will have a concrete offer on the table."
Hammond continued: "I would like to look at financial incentivisation for those employers for whom it matters. It would be direct financial incentivisation. It means cash - it means cash when their employees get called out on reserve service."
He added: "Now that does matter to small employers. If I talk to the large employers they're not interested in financial incentives. They do this because it's good for their business and because it's part of their corporate social responsibility."
Under the Coalition's defence review, the Territorial Army (TA) is expected to increase from 19,000 fully trained members to 30,000 by 2018, while the regular army is to be cut by 20,000 to 82,000.
