I'm just the same Nathan, hate doing it. Always last minute and then takes me the space of a week to finally submit it and pay it.

I pay for all things in shop or petrol station by card and any online orders by pay pal as already suggested.
As for the receipts my only suggestion ( that I haven't yet implemented myself ) is a bit of wood with a 6" nail hammered through it.
Each day you have receipts to file, stick em on it face down to keep them in order. File end of each month ( in my case - expenses in George ) and put in an envelope with that month written on it.
Now , if I only took my own advice