Over 170 new staff are needed to deal with the growing pressure on the tax system caused by massive increases in tax returns from all sectors of the economy, according to IMPACT, the trade union. It says that the number of Revenue staff dealing directly with tax assessment and enforcement has fallen by over 10 per cent since 1987, while corporation tax returns have increased by around 300 per cent and PAYE employee records by over 60 per cent in the same period.