If you're on OSD, the algorithms employed by Taxumo to fill out your income tax forms do not take the expenses into consideration. It's based on your Gross Sales/Receipts, after all.
However, we do recommend that you still enter your expenses because
regardless of what deduction method you choose, you will still need to enter your disbursements in your books of accounts. You can use Taxumo's Books of Accounts to see the expenses laid out in the proper format -- allowing you to easily copy them into your books using the format expected by the BIR.
In any case, do remember to make sure you still enter your Form 2307s (Certificates of Tax Withheld) so that these are still deducted from your tax due!