Are principal payments on government bonds included in normal budget spending? If I look, for example, at the UK government's Autumn 2017 budget document the spending piechart has a wedge which says 'net debt interest £41bn'. I notice the wording says 'interest' and not something like 'net debt servicing' or 'interest and principal'.  The government has to repay the principal amount of the bond when it matures.  My question is are these prinicpal payment included in normal budget spending?  If not where are they accounted for in government finances?  Thank you.
Normally, they aren’t, but there are exceptions. For example. The Japanese Ministry of Finance includes principal repayments in its definition of “debt service” - see budget summary for 2014, page 4.

(The inclusion of principal payments in debt service seems to be a convention for external debt: how much foreign currency debt that needs to be paid back can matter for credit risk. Floating currency sovereigns like the U.K. have negligible credit risk for their local currency borrowings.)

The reason why it is ignored principal repayment is a fairly meaningless number in government finance. If the government issues \$1 billion in short-term debt, in one year it will have:


(roughly) \$12 billion in principal repayments if it rolls over 1-month bills,
(roughly) \$4 billion in principal repayments if it rolls over 3-month bills, or
(roughly) \$1 billion in principal repayment if it issues a 12-month bill.
(Numbers are approximations since Treasury bills are discount instruments.)


The same principle works for longer-dated debt: you have twice the principal repayments if you roll over a 5-year bond instead of issuing a 10-year bond. 

So all principal payments tell us about is the debt management strategy of the government.

If you want to know how government debt is out there, you just look at the debt stock.