Sainsbury's projects an additional £140m in costs from upcoming National Insurance changes, with M&S forecasting £60m, both indicating likely price increases for consumers. The new NI rates, set to rise to 15% from April, are part of a broader government strategy to stabilize public finances but pose significant inflationary pressures on the retail sector. Executives from both companies cite challenges from rising costs within an already low-margin industry, further complicating their ability to maintain current price levels. Sainsbury's reports growth in grocery sales during consumer shifts toward dining in over eating out.