I have a spreadsheet to calculate Er's NI contributions per employee. I can't quite get the roundings right though, we're only talking a penny here and there but they all add up and my grand totals are often wrong.
For example, I have one employee who gets £145.92 per week gross. I calculate NI to be 145.92 - 144 = 1.92 x 13.8% = 0.26496. The HMRC calculator says it should be 0.26 so I assume they round down.
But, another employee gets £152.00. NI should be 152 - 144 = 8.00 x 13.8% = 1.104. If I round this down it is 1.10. But HMRC says it is 1.11
So can anyone help me with the exact way in which I should be calculating these?