"COMMON STOCK PURCHASE AGREEMENT" isn't a "term of art" that everybody knows and understands; I sure don't.
Many companies have employer stock incentive programs whereby employees get employer stock, or at least the opportunity to acquire employer stock, usually at a discount to market. Common terms for these plans includes "Restricted Stock", Restricted Stock Units, Restricted Stock Awards, Non-Qualified Stock Options, Incentive Stock Options, and Employee Stock Stock Purchase Plan.
If this COMMON STOCK PURCHASE AGREEMENT simply allows your husband to buy stock at the stock's fair market value at the date of purchase then I'd say you have nothing to report. Similar to buying stock in the open market through a broker, you don't report the simple "purchase" on your income tax return, you only report the purchase when you sell.
If this COMMON STOCK PURCHASE AGREEMENT allows purchase of stock at a discount and your husband can sell that stock at any time, generally the "spread" between the fair market value of the stock and the price paid is considered "compensation", reported on the W-2, though with some plans that compensation gets reported at the acquisition of the stock, but with other plans the compensation is triggered by the sale of the stock.
I'd advise reading that COMMON STOCK PURCHASE AGREEMENT and trying to get the gist of what's going on.
Tom Young