Budget season goes wrong in a predictable order, so it is worth doing in the opposite one.
Start from the reserve, not the operating fund
The reserve contribution is the number with a study behind it and the least room for negotiation. Set it first, from the funding plan, and treat it as fixed.
Boards that build the operating budget first and then find the reserve contribution from what is left have reversed the causation, and the reserve is what pays for it.
Then the contracts you cannot change
Insurance, utilities, the management or accounting fees if any, and every contract already in force. These are known and they set the floor.
Then the discretionary lines, against last year's actuals
Not against last year's budget. Budget against budget compounds every estimating error you have ever made.
Then the fee change falls out
The total divided by the allocation basis in the declaration gives the per unit contribution. It is arithmetic at that point, which is the whole reason for doing it in this order.
Then the notice
Owners have to receive the budget, and in Ontario they have to receive it before the year it covers begins. Florida associations adopt at a meeting owners were noticed for, with the proposed budget sent with the notice.
Work back from that date, not forward from today. It is the only fixed point in the process.
Write the covering note as though owners will read it
Most will not. The ones who do are the ones who would otherwise be at the annual meeting asking why. Two paragraphs, plainly written, on what changed and why, saves an evening.