The real issue under discussion here is a "tax loss carryforward". The concept here is that when a company suffers a tax loss in a fiscal year, the taxpayer may use the percentage set forth in tax legislation to reduce taxable income generated in future fiscal years. In Mexico, the carryforward period is 10 years, so this means that the taxpayer is allowed to reduce the taxable income generated each fiscal year by 10% over that 10 year period. You could say that the tax loss may be "carried forward" or "offset" against future taxable income. "Pérdida fiscal por amortizar" is how you say "tax loss carryforward" in the Spanish of Mexico. The text you are working with does not openly come out and specify a tax loss carryforward, but that is the essence of what is happening.
Reference: Accounting Trends & Techniques published by the AICPA annually.
More than 16 years of experience translating for Mexico City based member firms of international accounting firms (PwC, Grant Thornton, Instituto Mexicano de Contadores Públicos, A.C., etc.)
Hope this helps.

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Note added at 2005-04-15 04:18:20 (GMT) Post-grading
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Con mucho gusto. Saludos desde México, Richard