When converting LIFO earnings to FIFO, add the change in the LIFO reserve after tax: NI_FIFO = NI_LIFO + (Δ LIFO Reserve × (1 − t)). An increase in the reserve means LIFO COGS was higher, so FIFO income is higher. Cash taxes actually paid under LIFO are a real difference and need separate thought. Applying the full pre-tax reserve change to NI without tax is a planted error.