20 C.F.R. § 234.58
The separation allowance lump-sum payment is calculated as follows:
Example: In January of 1988 an employee with 10 years of railroad service relinquished his seniority rights in order to receive a separation allowance of $20,000, thereby severing his employment relation. This was the only creditable railroad compensation earned by the employee in 1988. Both the employer and employee would have paid their share of railroad retirement taxes on this amount. With respect to the employee tier II tax, the tax rate for 1988 was 4.9% under section 3201(b) of the Internal Revenue Code of 1986. Although the full $20,000 was creditable under the Railroad Retirement Act for tier I benefit computation purposes, only one month's compensation, $2,800, one-twelfth of the annual tier II earnings base of $33,600 for 1988, was creditable for tier II benefit purposes. This is because section 3(i)(4) of the Railroad Retirement Act does not permit crediting of compensation for tier II computation purposes after the employment relation has been severed. Under the lump-sum provision discussed above, the employee in this example would, upon award of his employee annuity, receive a payment of $842.80 ($20,000 minus $2,800, the amount of separation allowance that was creditable, or $17,200 times 4.9%).
20 C.F.R. §234.58