How can I get a YTD budget report from Quicken Mac that includes only full months?

Yes, this is a known — and significant — shortcoming in the budget functionality of Quicken Mac which the developers have inexplicably ignored for years. (But there's hope for the future! Read on.)

The only report to show budget versus actual is if you open your budget and print it. But that's not so useful, because it shows all 12 months, and it doesn't even total across the months.

The only place you can see year-to-date budget versus actual is in the columns to the right of the category names. (If your second column is January, click the "<<" icon to open the YTD columns; then click the "v" icon to toggle between Jan-December and Jan-current month.) Unfortunately, these columns don't print when you print the budget. Worse, as you've discovered, it always shows actual versus budget through the current month. So if you view it today, August 14, you're seeing actual income and expenses through mid-August and budget through the end of August; but what you likely want is to see is YTD through the end of the prior month (e.g. Jan 1-July 30) so you're comparing apples to apples. And there is no report to do that. So if you look on the last day of August, and all your transactions are up-to-date, you can view — but not print — your year-to-date through August. But don't sleep on August 31; if you wait until September 1 to look at it, the YTD column will be showing the budget through September, which you don't want. It's a gaping hole in the program.

If you're somewhat adept with a spreadsheet (Excel, Numbers, or Google Sheets), you can get the YTD report you want by exporting the budget, deleting the future months, summing the actual columns, summing the budget columns, creating a difference column, and then copying those cells down through all the rows, and totaling them. (Even totaling the columns its tricky because the budget rows show both main categories and subcategories, and you can't include both in your totals.) If you're comfortable with a spreadsheet, you can get there reasonably quickly. But it's annoying to have to build each month. 

If you're an advanced spreadsheet user, you can build a spreadsheet with formulas for each month such that so you just have to export the Quicken report and paste it into one sheet, select your month, and see a YTD report in another sheet. I have an Excel file with three sheets: the first is where I paste in the export from Quicken; the second builds 12 columns of YTD actuals and 12 columns of YTD budget values from the first sheet; the third is my YTD report where I enter the month number and it pulls the appropriate actual and budget values from the second sheet. This allows me to generate a YTD budget report in 5 seconds without needing to create or edit any formulas — but building such a spreadsheet requires some proficiency.

There is a long-running Idea thread requesting the ability to create and print an actual versus budget report for a user-specified date range which you can read here. The good news is that the developers have finally marked this as "Planned", meaning they "get it" and have it on their roadmap — we just never know how long it will take until a Planned feature is completed and appears in the program.