There are very few allowable adjustments to gross income for business tax reporting purposes. However, the Income and Business Tax Act does allows adjustment for charitable contributions against your gross revenues in the month of December. Kindly note the following extract from the Income Tax Department publication:
The Business Tax Act allows the following adjustments to your receipts to arrive at the total revenues you are to pay tax on:
Gifts aggregating $500 or more, taking effect in Belize, for Sports, Religious, Charitable, Educational or Cultural purposes or for the improvement of amenities in Towns or Villages, up to a maximum of $30,000 per annum. Original receipts/acknowledgments must be submitted for the Commissioner to be satisfied that the payments were actually made.
This is supported by section 105 (viii) of the Income and Business tax act which is similar in text and states:
absolute and immediate gifts amounting in the aggregate to five hundred dollars or more, taking effect in Belize, for sports, religious, charitable, educational or cultural purposes or for the improvement of amenities in towns or villages, up to a maximum of $30,000 per annum, provided that the Commissioner is satisfied that the gifts were
Note that the Income and Business Tax Act does not state that this offset is to happen only in December rather the Income Tax Department has decided to implement it as a policy for easier administration.