As part of the new cost basis reporting rules, corporations are now required by law to inform their stockholders how to calculate adjustments to their cost basis caused by corporate actions such as splits, spinoffs, issuance of stock rights, mergers, etc. Corporations are also now required to file a new Form 8937 "Report of Organizational Actions Affecting Basis of Securities" with the IRS. This information must be provided no later than January 15 of the next calendar year or 45 days after the corporate action, whichever is earlier.
Companies may meet this disclosure requirement by posting the information on their website. The information must remain publicly available for ten years. Every tax accountant in the country is thankful for this useful new common sense requirement which will make life easier.
Many companies will simply post the Form 8937 itself. The relevant section to look for is line 15 where the cost allocation percentages will be given.