Research and Experimentation Advances Competitiveness at Home Act or the REACH Act This bill amends the Internal Revenue Code, with respect to the tax credit for increasing research activities (known as the research and experimentation tax credit), to: increase the alternative simplified credit rate to match the rate of the regular credit; allow taxpayers to use reasonable estimation techniques in lieu of contemporaneous accounting to measure employee hours per business component; allow employees engaging in the direct supervision or direct support of research activities which constitute qualified research to be included in the research expense calculation without regard to the employee's position or management level; allow the credit to be used for research related to the adaptation of an existing business component to a particular customer's requirement or need, cost reduction, or obsolescence mitigation; and allow taxpayers to make an election for a reduced credit (in order to be allowed a full deduction for research expenses) on an amended tax return.