HST remittance formula

[Ron Stone]

Hello all,

First - I am fairly new to GnuCash and, having heard about it for years, wish I’d started sooner. It is a robust app and my hat is off to everyone who has contributed. 

My question is about Canadian HST (Harmonized Sales Tax) - a combination of provincial sales tax and federal GST collected and administered together in some provinces.

Small businesses can elect to use a ‘simple method’ for calculating the HST they need to remit at the end of each period (in my case every quarter). Instead of tracking every sale and every purchase to come up with a number, they can remit a percentage based on total sales. 
For example, in Ontario HST is 13%. The quick method might require that I remit 7.5% of total sales. For businesses such as consultants who do not have a lot of purchases, it means you actually keep some of the HST (which becomes taxable income). 

The 7.5% above was just a number to illustrate, but there is a wrinkle. For most businesses (mine at least), the percentage you remit is lower on the first $30,000 and then jumps on the rest of your income for the year. Say, >=30k = 7.5%, and <$30k=8.5.

My question is if a formula could be written for a scheduled transaction to calculate what I owe at the end of each quarter and what I’ll have to track as income on my business taxes (the amount from the HST collected that I remit and the amount that I keep). I have not seen any examples of querying account data from a script, so I’m not sure if it is doable. You would need to know how much you have sold in the past quarter and how much of that is above/below the $30k threshold. 

I am using 2.6.3. 

If it is doable, and anyone cares to lend their expertise, it may help document some powerful features of Gnucash.

Many thanks,
Ron