Britain’s sixth largest accountancy practice BDO Stoy Hayward has agreed to buy Chiltern, which is the country’s biggest tax only business. The move, which is the latest example of consolidation in the mid-tier of Britain’s accountancy practices, follows fifth-placed Grant Thornton’s takeover of RSM Robson Rhodes in July. Grant Thornton and BDO Stoy Hayward are the only serious challengers to the Big Four firms and have picked up larger businesses as clients seeking to diversify advisers in the wake of Enron. Chiltern recently ended its relationship with another accountancy practice Moores Rowland which within weeks was taken over by another firm. Chiltern then restyled itself as a tax-only practice. It has been marketing itself aggressively in this role. BDO’s income in the current year was £330 million. Chiltern’s turnover was £20 million in the same period. Although this merger will mean that BDO edges closer to Grant Thornton, GT will be £40 million a year ahead. In the short-term, Chiltern's staff will remain at their Paddington office and continue to trade under the Chiltern brand. They are expected to move to BDO's new London premises at 55 Baker Street early next year.