Are you asking about the Loss Netting on the 8995-A, Schedule C? Lacerte does a fine job of that, and its calculations agree with my Excel file.

Or are you asking about the current-year QBI losses disallowed / prior year disallowed QBI losses allowed in the current year? The statutory calculation of those is unintuitive, but there are worksheets that show you exactly how Lacerte does the math. They come after state refunds taxable in current year, state refunds taxable in subsequent year, and taxable Social Security worksheets, and before the Qualified Dividends and Capital Gains worksheet. My clients with them have 3 sets of calculations: Qualified Business Income, QBI Losses Disallowed, and Prior Year Disallowed QBI Losses Allowed in Current Year. I don't bother proofing them in Excel, because Lacerte appears to be doing it correctly and it involves having multiple categories of passive losses and QBI losses carried forward by year since 2018.